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

The ODBII 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.

The severity of ODBII code B1904 is typically considered moderate to high.

Common Causes For: B1903 Air Bag Crash Sensor #1 Ground Circuit Short To Battery

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

• 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

Common Troubleshooting Steps

When dealing with OBD-II code B1904, which indicates a failure in the airbag crash sensor #2 feed/return circuit, it’s important to follow a systematic approach to troubleshoot the issue. Here are common troubleshooting steps:

• Scan Tool Verification:
• Use an OBD-II scanner to confirm the presence of the B1904 code. Check for any additional codes that may provide more context.
• Visual Inspection:
• Inspect the wiring and connectors associated with the airbag crash sensor #2. Look for signs of damage, corrosion, or loose connections.
• Check the sensor itself for physical damage.
• Check the Sensor:
• 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.
• Inspect the Circuit:
• Use a multimeter to check the continuity of the feed and return circuits. Look for any breaks or shorts in the wiring.
• Check for proper voltage at the sensor connector with the ignition on. Compare the readings to the specifications in the service manual.
• Check Ground Connections:
• Ensure that the ground connections for the airbag system are secure and free of corrosion. A poor ground can cause circuit failures.
• Test the Airbag Module:
• 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.
• Clear Codes and Test Drive:
• 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.
• Consult Technical Service Bulletins (TSBs):
• 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.
• Professional Diagnosis:
• 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.