WOMS
P code powertrain Medium severity

P1108 Dual Alternator Battery Lamp Circuit Malfunction

The OBD2 code P1108 indicates a malfunction in the dual alternator battery lamp circuit, which may affect the charging system and battery performance

Definition

The OBD2 code P1108 indicates a malfunction in the dual alternator battery lamp circuit, which may affect the charging system and battery performance

Common causes

  • Faulty alternator
  • Bad battery
  • Damaged wiring or connectors
  • Failed battery lamp
  • Faulty voltage regulator
  • Poor ground connection
  • Malfunctioning engine control module (ECM)

Common misdiagnoses

  • Faulty alternator
  • Bad battery
  • Wiring issues
  • Faulty battery lamp
  • Malfunctioning voltage regulator
  • Poor ground connections
  • Incorrectly installed or damaged connectors

Troubleshooting steps

  1. 1. Check the Battery:

    Voltage Test: Use a multimeter to check the battery voltage. A healthy battery should read around 12.6 volts or more when the engine is off

  2. 2. Load Test

    Perform a load test on the battery to ensure it can hold a charge under load

  3. 3. Inspect the Alternators:

    Visual Inspection: Check both alternators for any signs of damage, loose connections, or corrosion

  4. 4. Output Test

    Use a multimeter to measure the output voltage of each alternator while the engine is running. It should typically be between 13.5 to 14.5 volts

  5. 5. Check Wiring and Connectors:

    Inspect Wiring: Look for damaged, frayed, or corroded wires in the battery lamp circuit and alternator connections

  6. 6. Connector Condition

    Ensure that all connectors are clean, tight, and free of corrosion

  7. 7. Examine the Battery Lamp Circuit:

    Lamp Functionality: Check if the battery warning light on the dashboard illuminates when the ignition is turned on. If it does not, the bulb may be burned out or there may be a circuit issue

  8. 8. Circuit Continuity

    Use a multimeter to check for continuity in the battery lamp circuit. Look for any breaks or shorts

  9. 9. Check the Voltage Regulator:

    Regulator Functionality: If the vehicle has an external voltage regulator, test it to ensure it is functioning correctly. If it is integrated into the alternator, consider testing or replacing the alternator

  10. 10. Scan for Additional Codes:

    Check for Other Codes: Use an OBD-II scanner to check for any other related trouble codes that may provide additional context for the issue

  11. 11. Inspect the Engine Control Module (ECM):

    ECM Functionality: In some cases, the ECM may be at fault. Check for any software updates or known issues related to the ECM

  12. 12. Clear Codes and Test Drive:

    After performing the above checks and repairs, clear the trouble codes using an OBD-II scanner and take the vehicle for a test drive to see if the code returns

  13. 13. Seek Professional Help:

    If you are unable to resolve the issue after these steps, consider consulting a professional mechanic for further diagnosis and repair. By following these steps, you should be able to identify and resolve the issue related to the P1108 code