Code
P1138
ALFA ROMEO
P — Powertrain
Diesel pressure circuit fault
Views:
UK: 4
EN: 5
RU: 4
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
BMW
P — Powertrain
O2 Sensor Heater Circuit Low Voltage Bank 1 Sensor 2
Views:
UK: 17
EN: 25
RU: 21
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
BUICK
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 20
EN: 28
RU: 22
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
CADILLAC
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 16
EN: 21
RU: 20
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
CHEVROLET
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 19
EN: 27
RU: 24
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
CHRYSLER
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 22
EN: 24
RU: 21
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
FIAT
P — Powertrain
Diesel pressure circuit fault
Views:
UK: 4
EN: 4
RU: 3
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
FORD
P — Powertrain
Lack of Downstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1
Views:
UK: 20
EN: 24
RU: 24
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
GM
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 18
EN: 25
RU: 24
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
GMC
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 18
EN: 23
RU: 22
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
HUMMER
P — Powertrain
Heated Oxygen Sensor (HO2S) Bank 1 Sensor 2 Rich or High Voltage
Views:
UK: 8
EN: 9
RU: 11
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
JAGUAR
P — Powertrain
Lack Of HO2S12 Switches Sensor Indicates Rich
Views:
UK: 19
EN: 25
RU: 22
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
LAND ROVER
P — Powertrain
Lack of key H02S-12, sensor indicates rich
Views:
UK: 5
EN: 8
RU: 7
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop ManualLand Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualLand Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop ManualYour experience will help others
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Code
P1138
LINCOLN
P — Powertrain
Lack of Downstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1
Views:
UK: 21
EN: 32
RU: 24
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
MAZDA
P — Powertrain
HO2S Bank 1 Sensor 2 Signal Above 0.45v AF Ratio Too Rich
Views:
UK: 20
EN: 27
RU: 22
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
MERCURY
P — Powertrain
Lack of Downstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 1
Views:
UK: 15
EN: 29
RU: 24
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
OLDSMOBILE
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 20
EN: 25
RU: 23
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
Other
P — Powertrain
Lack Of HO2S12 Switch - Sensor Indicates Rich
Views:
UK: 16
EN: 21
RU: 26
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Workshop ManualYour experience will help others
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Code
P1138
RAM
P — Powertrain
O2 Sensor Heater 2/1 Element Resistance Out of Range
Views:
UK: 1
EN: 3
RU: 2
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P1138
SAAB
P — Powertrain
Additive Adaptation Bank 2 Min Value Air/Fuel Mixture Too Rich
Views:
UK: 1
EN: 5
RU: 3
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
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Code
P1138
SATURN
P — Powertrain
HO2S Bank 1 Sensor 2 Rich Or High Voltage
Views:
UK: 16
EN: 29
RU: 25
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
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Code
P1138
VOLKSWAGEN
P — Powertrain
Long Term Fuel Trim Add Fuel Bank 2 System Too Lean
Views:
UK: 19
EN: 26
RU: 24
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or disconnected fuel rail pressure sensor connector or wiring (open, short to ground or to battery)
- Faulty fuel rail pressure sensor (incorrect output or intermittent)
- Faulty fuel pressure control valve (PCV) / pressure regulator or its control wiring
- Weak or failed low-pressure (lift) pump or high-pressure pump
- Fuel system contamination or clogged fuel filter limiting flow
- Fuel rail leak or leaking injector(s)
Symptoms
- Check Engine MIL illuminated
- Reduced engine power or limp mode
- Hard starting, extended cranking or no-start
- Rough idle or stalling
- Poor acceleration or hesitation
- Possible increased fuel use or smoke from exhaust
What to check
- Read stored freeze-frame and live data with a capable scan tool; note related codes
- Inspect sensor connector and wiring for corrosion, damage, loose pins and water ingress
- Check fuses and relays related to fuel pump and engine control circuits
- Verify vehicle fuel level and look for signs of contaminated fuel
- Backprobe sensor connector to verify reference voltage (usually 5V), ground continuity and signal
- Check fuel rail pressure with a calibrated mechanical or digital rail pressure gauge
Signal parameters
- Typical sensor reference supply: ~5 V (verify OEM spec for exact value)
- Typical signal output: nominally about 0.5–4.5 V across pressure range (low to high) — consult OEM for exact calibration
- Sensor ground: low resistance to chassis ground
- Live-data: commanded rail pressure vs actual should track closely; large deviation or fixed values indicate fault
- Rail pressure absolute values vary by engine; confirm expected idle and max pressure from manufacturer service data
Diagnostic algorithm
- Safety first: park on level surface, apply parking brake, relieve fuel system pressure per OEM procedures before disconnecting components.
- Connect a diagnostic scanner, read/record all codes and freeze-frame. Note any related fuel system or injector codes.
- Visually inspect the pressure sensor and harness. Repair any obvious connector or wiring damage before further testing.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage, ground continuity and signal voltage. Compare to OEM spec.
- If reference or ground absent or unstable, trace and repair wiring, fuses, relays, or grounds. Re-test after repair.
- If voltages are correct but signal is out of range or intermittent, swap with a known-good sensor (if available) or bench-test/replace the sensor.
- Install a calibrated fuel rail pressure gauge and compare actual rail pressure to ECU live data and commanded pressure during cranking and idle. Note discrepancies.
- If actual pressure is low or does not follow commanded changes, inspect/test pressure control valve/regulator and high-pressure pump operation.
- Check lift pump and fuel supply (filter, lines) for restrictions that can prevent adequate feed to high-pressure pump.
- If wiring and sensors check good and rail pressure instrumented testing shows correct mechanical operation, consider ECU diagnosis or update (check for TSBs).
- After repairs, clear codes and perform a road test and re-scan to confirm the fault does not return.
Likely causes
- Wiring/connectors to the rail pressure sensor (corrosion, chafing, pin pushed out)
- Failed or degraded fuel rail pressure sensor
- Pressure control valve (regulator) stuck or electrically failing
- Supply issue from lift pump or clogged filter reducing rail pressure
- High-pressure pump wear or internal leak
Fault status
Status
Fuel rail pressure circuit fault detected — sensor signal or circuit is out of range or intermittent. Fuel rail pressure may be incorrect, causing drivability issues.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
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Was this AI description helpful?
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