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B1555 Ignition Run/Start Circuit Failure

The OBD2 code B1555 indicates a failure in the ignition run/start circuit, which may involve issues with the ignition switch, wiring, or related components affecting the vehicle's ability to start or run properly

Definition

The OBD2 code B1555 indicates a failure in the ignition run/start circuit, which may involve issues with the ignition switch, wiring, or related components affecting the vehicle's ability to start or run properly

Common causes

  • Faulty ignition switch
  • Damaged wiring or connectors in the ignition circuit
  • Failed powertrain control module (PCM)
  • Short circuit in the ignition run/start circuit
  • Poor ground connection
  • Malfunctioning relay
  • Issues with the body control module (BCM)

Common misdiagnoses

  • Faulty ignition switch
  • Bad battery connections
  • Defective starter motor
  • Malfunctioning fuel pump
  • Wiring issues or shorts in the ignition circuit
  • Faulty body control module (BCM)
  • Defective relay or fuse
  • Issues with the anti-theft system
  • Faulty key or key fob
  • Problems with the engine control module (ECM)

Troubleshooting steps

  1. 1. Check the Battery

  2. 2. Ensure the battery is fully charged and in good condition. A weak battery can cause various electrical issues

  3. 3. Inspect Fuses

  4. 4. Check the fuses related to the ignition system. A blown fuse can interrupt the circuit and trigger the code

  5. 5. Examine Wiring and Connectors

  6. 6. Inspect the wiring and connectors associated with the ignition system for any signs of damage, corrosion, or loose connections. Pay special attention to the ignition switch and any related harnesses

  7. 7. Test the Ignition Switch

  8. 8. The ignition switch itself may be faulty. Use a multimeter to test the switch for continuity in the run and start positions

  9. 9. Check for Ground Issues

  10. 10. Ensure that all ground connections related to the ignition system are secure and free of corrosion. Poor grounding can lead to circuit failures

  11. 11. Scan for Additional Codes

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

  13. 13. Inspect the PCM (Powertrain Control Module)

  14. 14. In some cases, the PCM may be at fault. Check for any software updates or known issues with the PCM for your specific vehicle model

  15. 15. Test the Ignition Relay

  16. 16. If your vehicle uses an ignition relay, test it to ensure it is functioning properly. A faulty relay can prevent the ignition system from operating correctly

  17. 17. Check for Short Circuits

  18. 18. Look for any short circuits in the ignition wiring that could be causing the failure. This may require a more in-depth inspection of the wiring harness

  19. 19. Consult Vehicle-Specific Repair Manuals

  20. 20. Refer to the vehicle's service manual for specific diagnostic procedures and wiring diagrams related to the ignition system. 1

  21. 21. Professional Diagnosis

  22. 22. If the issue persists after performing the above steps, consider seeking help from a professional mechanic or technician who has experience with your vehicle make and model. By following these troubleshooting steps, you should be able to identify and resolve the issue causing the B1555 code. Always remember to take necessary safety precautions when working on vehicle electrical systems