B1904: Air Bag Crash Sensor #2 Feed/Return Circuit Failure
CriticalBodyRestraint System
What does B1904 mean?
B1904 is a diagnostic trouble code indicating "Air Bag Crash Sensor #2 Feed/Return Circuit Failure". A sensor in the restraint system is reporting abnormal data or has lost communication with the ECU. Sensors can fail due to age, contamination, heat exposure, or wiring issues.
Common causes
- Faulty restraint system component
- Wiring or connector issue in the related circuit
- Failed sensor providing incorrect readings
- Software/calibration issue requiring ECU update
- Related component causing secondary fault
What should you do?
This is a critical issue. Stop driving as soon as it is safe to do so and have the vehicle inspected immediately. Continuing to drive could cause further damage or pose a safety risk.
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Code B1904 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.