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B1904 Air Bag Crash Sensor #2 Feed/Return Circuit Failure

The OBD2 code B1904 indicates a malfunction in the feed or return circuit of Air Bag Crash Sensor #2, which may affect the airbag system's ability to deploy properly in the event of a collision

Definition

The OBD2 code B1904 indicates a malfunction in the feed or return circuit of Air Bag Crash Sensor #2, which may affect the airbag system's ability to deploy properly in the event of a collision

Common causes

  • Faulty airbag crash sensor
  • Damaged wiring or connectors
  • Poor electrical connections
  • Short circuit in the feed/return circuit
  • Open circuit in the feed/return circuit
  • Corrosion in connectors or wiring
  • Faulty airbag control module
  • Software issues in the airbag system

Common misdiagnoses

  • Faulty airbag module
  • Defective airbag sensor
  • Wiring issues unrelated to the crash sensor
  • Faulty seatbelt pretensioner
  • Malfunctioning body control module (BCM)
  • Incorrectly installed or damaged airbag system components
  • Battery or power supply issues affecting the airbag system

Troubleshooting steps

  1. 1. Scan Tool Verification

  2. 2. Use an OBD-II scanner to confirm the presence of the B1904 code. Check for any additional codes that may provide more context

  3. 3. Visual Inspection

  4. 4. Inspect the wiring and connectors associated with the airbag crash sensor #2. Look for signs of damage, corrosion, or loose connections

  5. 5. Check the sensor itself for physical damage

  6. 6. Check the Sensor

  7. 7. If accessible, test the airbag crash sensor #2 for proper operation. This may involve checking resistance or voltage as specified in the vehicle's service manual

  8. 8. Inspect the Circuit

  9. 9. Use a multimeter to check the continuity of the feed and return circuits. Look for any breaks or shorts in the wiring

  10. 10. Check for proper voltage at the sensor connector with the ignition on. Compare the readings to the specifications in the service manual

  11. 11. Check Ground Connections

  12. 12. Ensure that the ground connections for the airbag system are secure and free of corrosion. A poor ground can cause circuit failures

  13. 13. Test the Airbag Module

  14. 14. If the sensor and wiring appear to be in good condition, the issue may lie within the airbag control module. Testing or replacing the module may be necessary

  15. 15. Clear Codes and Test Drive

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

  17. 17. Consult Technical Service Bulletins (TSBs)

  18. 18. Check for any TSBs related to the airbag system for your specific vehicle make and model. There may be known issues or recalls that could be relevant

  19. 19. Professional Diagnosis

  20. 20. If the problem persists after following these steps, consider seeking help from a professional technician who specializes in automotive electrical systems or airbag systems.Safety Note: Working with airbag systems can be dangerous. Always follow safety precautions, such as disconnecting the battery and waiting for a specified time before working on the airbag system. If you're unsure or uncomfortable with any step, it's best to consult a professional