Code
P1691
ALFA ROMEO
P — Powertrain
Safety shutdown fault
Views:
UK: 5
EN: 6
RU: 6
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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Code
P1691
BUICK
P — Powertrain
Coolant Gage Circuit Low Voltage
Views:
UK: 19
EN: 25
RU: 17
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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Code
P1691
CADILLAC
P — Powertrain
Coolant Gage Circuit Low Voltage
Views:
UK: 15
EN: 27
RU: 26
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
CHEVROLET
P — Powertrain
Coolant Gage Circuit Low Voltage
Views:
UK: 17
EN: 23
RU: 17
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
CHRYSLER
P — Powertrain
Fuel Injection Pump Controller Calibration Failure
Views:
UK: 17
EN: 26
RU: 22
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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+100 karma for a short comment :)
Was this AI description helpful?
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Code
P1691
DODGE
P — Powertrain
Fuel Injection Pump Controller Calibration Failure
Views:
UK: 14
EN: 26
RU: 20
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
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Send to email
Code
P1691
FIAT
P — Powertrain
Safety shutdown fault
Views:
UK: 5
EN: 6
RU: 7
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
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Send to email
Code
P1691
GM
P — Powertrain
Coolant Gage Circuit Low Voltage
Views:
UK: 16
EN: 23
RU: 20
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
GMC
P — Powertrain
Coolant Gage Circuit Low Voltage
Views:
UK: 18
EN: 28
RU: 20
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
HUMMER
P — Powertrain
Coolant Gage Circuit Low Voltage
Views:
UK: 9
EN: 19
RU: 12
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
JEEP
P — Powertrain
Fuel Injection Pump Controller Calibration Failure
Views:
UK: 20
EN: 26
RU: 21
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
MAZDA
P — Powertrain
Turbo Pressure Control Solenoid Circuit
Views:
UK: 18
EN: 26
RU: 18
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
MINI
P — Powertrain
Electronic throttle control monitor level 2/3 - motorised throttle control engine speed limitation error
Views:
UK: 3
EN: 2
RU: 3
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
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Code
P1691
OLDSMOBILE
P — Powertrain
Coolant Gauge Circuit Low Voltage
Views:
UK: 21
EN: 26
RU: 19
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
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0
Send to email
Code
P1691
Other
P — Powertrain
Turbo Pressure Control Solenoid Circuit Malfunction
Views:
UK: 24
EN: 32
RU: 28
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
PLYMOUTH
P — Powertrain
Fuel Injection Pump Controller Calibration Failure
Views:
UK: 15
EN: 26
RU: 20
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P1691
PONTIAC
P — Powertrain
Fuel Injection Pump Controller Calibration Failure
Views:
UK: 19
EN: 25
RU: 21
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
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Code
P1691
PORSCHE
P — Powertrain
MIL (Check Engine)
Views:
UK: 5
EN: 4
RU: 5
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
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0
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Code
P1691
SAAB
P — Powertrain
Check Engine Light Open Circuit
Views:
UK: 3
EN: 3
RU: 6
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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👍 Like
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Code
P1691
SATURN
P — Powertrain
Coolant Gage Circuit Low Voltage
Views:
UK: 19
EN: 28
RU: 24
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
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0
Send to email
Code
P1691
VOLKSWAGEN
P — Powertrain
MIL Open Circuit
Views:
UK: 20
EN: 25
RU: 24
AI status
Completed
Completed
100%
Causes
- Engine overtemperature
- Critically low oil pressure
- Severe low fuel pressure or loss of fuel supply
- Loss of power or ground to ECU or key engine management circuits
- Persistent sensor faults (coolant temp, oil pressure, fuel rail pressure)
- Intermittent or lost communication on vehicle communication buses (CAN)
Symptoms
- Engine shuts down unexpectedly or refuses to restart after a shutdown
- Reduced engine power / limp-home mode
- MIL/engine warning light illuminated
- Other related DTCs present (temperature, pressure, voltage, communication codes)
- No-start with starter cranking but engine stalls immediately
- Instrument cluster warnings (immobilizer, battery, temperature)
What to check
- Read and record all stored DTCs and freeze-frame data with a capable scan tool
- Check battery voltage with ignition ON and during cranking (should be ~12.4–12.7 V at rest, >10 V while cranking)
- Inspect charging system (alternator output ~13.5–14.8 V with engine running)
- Visual inspection of fuses, engine ECU power/ground connections and relevant relays
- Check engine coolant level and oil level; look for leaks and the presence of overheating
- Verify fuel level and listen for fuel pump operation when key is turned to ON
Signal parameters
- Battery voltage (key ON, engine OFF): expected ~12.4–12.7 V
- Charging voltage (engine running): expected ~13.5–14.8 V
- Engine coolant temp (ECT): normal operating ~80–105 °C; check for sudden spikes
- Oil pressure or oil pressure sensor voltage: varies by engine—verify against manufacturer spec
- Fuel rail/line pressure: static and commanded pressures per vehicle spec (common rails often 200–1600 bar; port-injection lower)
- Engine RPM during event: stalling/zero or sudden drop
Diagnostic algorithm
- Connect a full-function scan tool and retrieve all active and stored codes plus freeze-frame data. Note time, engine conditions, and other fault codes recorded with P1691.
- Do not assume a single cause. Correlate freeze-frame values: coolant temp, oil pressure, fuel pressure, battery voltage, RPM at event.
- Verify battery and charging system health. Perform voltage tests at battery and at ECU power and ground pins. Repair poor battery/charging faults and retest.
- Check engine oil level and pressure. If low or suspect, measure oil pressure with a mechanical gauge. Repair leaks or oil pump issues as needed.
- Check coolant level and temperature sensor operation. Inspect cooling system for thermostat or cooling fan failures. Replace faulty sensors or components found.
- Inspect fuel delivery: confirm fuel pump operation, fuel pressure and fuel filter condition. Repair fuel supply faults and clear codes.
- Inspect fuses, relays and wiring for ECU power/ground and sensor circuits. Wiggle-test connectors and look for corrosion or damaged pins.
- Scan for communication faults. If CAN/communication errors exist, trace wiring and module connections; repair bus issues and re-scan.
- Check immobilizer/security system messages. If security module requested shutdown, follow manufacturer procedure to reprogram or sync modules.
- If no clear external cause is found and power/ground and communications are good, check for ECU software updates or known bulletins. Consider ECU reflash before replacement.
- After repairs, clear codes and attempt to reproduce. If P1691 returns, document conditions and escalate with manufacturer technical support for advanced diagnostics or ECU bench testing.
Likely causes
- Low battery/charging system problem causing voltage dropout to ECU
- Faulty coolant temperature sensor reporting overtemperature
- Failed oil pressure sensor or actual low oil pressure
- Broken wiring, poor connector or blown fuse/relay in engine management power/ground circuits
- Fuel pump failure or fuel rail pressure sensor/circuit fault
- Previous related DTCs that triggered protective shutdown (look for multiple codes)
Fault status
Status
Safety shutdown detected by ECU — protective engine shutoff or limp mode triggered due to a critical condition or sensor/communication fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email