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Home / DTC / P1674 — Voltage condition 2 fault

P1674 — Voltage condition 2 fault

Detailed page for trouble code P1674.

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Code

P1674

ALFA ROMEO P — Powertrain

Voltage condition 2 fault

Brand: ALFA ROMEO
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
89

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Code

P1674

BUICK P — Powertrain

Tachometer Control Circuit

Brand: BUICK
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
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Code

P1674

CADILLAC P — Powertrain

Tachometer Control Circuit

Brand: CADILLAC
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
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Code

P1674

CHEVROLET P — Powertrain

Tachometer Control Circuit

Brand: CHEVROLET
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
410

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Code

P1674

DAEWOO P — Powertrain

A/c fan relay

Brand: DAEWOO
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
Repair manuals

Manual library for DAEWOO

75

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Code

P1674

FIAT P — Powertrain

Voltage condition 2 fault

Brand: FIAT
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
Repair manuals

Manual library for FIAT

26

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Code

P1674

GM P — Powertrain

Tachometer Control Circuit

Brand: GM
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email
Code

P1674

GMC P — Powertrain

Tachometer Control Circuit

Brand: GMC
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
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Code

P1674

HUMMER P — Powertrain

Tachometer Control Circuit

Brand: HUMMER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
Repair manuals

Manual library for HUMMER

138

Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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Code

P1674

LAND ROVER P — Powertrain

Corrupted control module software

Brand: LAND ROVER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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Code

P1674

OLDSMOBILE P — Powertrain

Tachometer Control Circuit

Brand: OLDSMOBILE
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email
Code

P1674

RAM P — Powertrain

Mass Air Flow Sensor Supply

Brand: RAM
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email
Code

P1674

SATURN P — Powertrain

Tachometer Control Circuit

Brand: SATURN
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or discharged battery
  • Poor battery terminal connections or corroded clamps
  • Defective or slipping alternator or voltage regulator
  • Damaged, loose or corroded main power or ground wiring to the ECU
  • Blown or intermittent main power fuse/relay
  • High resistance in harness connectors or inline fusible links

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Intermittent engine stalling, hesitation or poor running
  • Hard starting or no-crank/no-start conditions
  • Dimming or flickering dashboard and exterior lights
  • Loss or intermittent faults in other electronically controlled systems
  • Possible communication errors with diagnostic tool

What to check

  • Read and record freeze frame and live data with a capable scan tool; note voltage values when the code set
  • Check battery resting voltage (key off), cranking voltage and charging voltage at idle and at 2,000–3,000 rpm
  • Visually inspect battery terminals, cables and ground straps for corrosion, looseness or damage
  • Inspect main power/ground wiring to the ECU and related fuses, fusible links and relays
  • Perform a battery load test and alternator output/diode check
  • Wiggle-test wiring and connectors while monitoring voltage/live data for intermittent faults

Signal parameters

  • Battery resting voltage: typically ~12.4–12.8 V (vehicle-specific tolerances apply)
  • Cranking voltage: usually above ~9–10 V depending on starter and battery condition
  • Charging voltage (engine running): nominally ~13.5–14.8 V
  • ECU internal monitored supply: expected to remain within manufacturer-specified range and free of rapid spikes/transients
  • Fault set when monitored vehicle/ECU supply is outside allowable range or exhibits abnormal transients

Diagnostic algorithm

  1. Use a scan tool to confirm code P1674, record freeze-frame data and related codes. Clear codes and attempt to reproduce.
  2. Visually inspect battery, cables, terminals, main ground straps and ECU power connectors. Repair or clean as required.
  3. Measure battery voltage (key off), during crank and with engine running. Compare to expected ranges and record results.
  4. Perform a battery load test. If battery fails, replace battery and retest.
  5. Test alternator output and regulator under load (voltage at idle and at higher RPM, check for excessive ripple or diode failure). Repair or replace alternator if out of spec.
  6. Inspect and test fuses, fusible links, main power relay and wiring between battery, alternator and ECU for high resistance, damage or intermittent connection. Repair broken wires, corroded terminals and poor grounds.
  7. With a DMM and oscilloscope if available, monitor ECU supply for voltage spikes/transients while reproducing the condition. Address transient sources (ignition, aftermarket devices, poor grounds).
  8. After repairs, clear codes and verify the issue cannot be reproduced; road test and re-scan. If all wiring and charging/battery systems test good and fault persists, consider ECU fault and consult manufacturer procedures before replacement.

Likely causes

  • Low battery voltage under load (battery failing or poor connections)
  • Intermittent charging system (alternator/regulator) producing undervoltage/overvoltage or spikes
  • Bad battery ground or ECU ground strap causing voltage drops
  • Loose or corroded main power connector at the ECU or under-hood junction
  • Temporary voltage transient due to jump start or poor charging system regulation

Fault status

⚠️ Status
Voltage condition 2 fault — vehicle/ECU supply voltage outside expected range or experiencing abnormal transient; ECM set DTC P1674.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3 hours
Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

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