WOMS
P code powertrain Medium severity

P1246 Alternator Load Input Failed

The OBD2 code P1246 indicates that the alternator load input signal is not functioning properly, which may affect the vehicle's charging system and overall electrical performance

Definition

The OBD2 code P1246 indicates that the alternator load input signal is not functioning properly, which may affect the vehicle's charging system and overall electrical performance

Common causes

  • Faulty alternator
  • Bad alternator connections or wiring
  • Failed battery
  • Faulty engine control module (ECM)
  • Corroded or damaged connectors
  • Issues with the voltage regulator
  • Faulty sensors related to alternator load
  • Electrical system issues (e.g., shorts or opens in the circuit)

Common misdiagnoses

  • Faulty alternator
  • Bad battery
  • Wiring issues
  • Faulty PCM (Powertrain Control Module)
  • Bad ground connections
  • Faulty voltage regulator
  • Sensor issues (e.g., throttle position sensor)
  • Electrical shorts or open circuits
  • Incorrectly diagnosed charging system problems
  • Issues with the engine control module (ECM)

Troubleshooting steps

  1. 1. Check the Battery:

    Ensure the battery is fully charged and in good condition. A weak or failing battery can cause issues with the alternator's performance

  2. 2. Inspect the Alternator:

    Check the alternator for any physical damage or signs of wear

  3. 3. Ensure that the alternator belt is in good condition and properly tensioned

  4. 4. Test the Alternator Output:

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

  5. 5. If the output is low, the alternator may be failing and may need to be replaced

  6. 6. Check Wiring and Connectors:

    Inspect the wiring and connectors between the alternator and the ECM for any signs of damage, corrosion, or loose connections

  7. 7. Pay special attention to the alternator load input wire

  8. 8. Scan for Additional Codes:

    Use an OBD-II scanner to check for any other related trouble codes that may provide more context to the issue

  9. 9. Inspect the ECM:

    In rare cases, the ECM itself may be faulty. Check for any signs of damage or corrosion on the ECM connectors

  10. 10. If necessary, perform a software update or reset the ECM

  11. 11. Check for Ground Issues:

    Ensure that the alternator and ECM have a good ground connection. Poor grounding can lead to communication issues

  12. 12. Perform a Load Test:

    Conduct a load test on the alternator to see if it can handle the electrical load of the vehicle. This can help identify if the alternator is underperforming

  13. 13. Clear Codes and Test Drive:

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

  14. 14. Consult a Professional:

    If the issue persists after performing these steps, it may be best to consult a professional mechanic for further diagnosis. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P1246 code