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.
Symptoms you may notice
- Check engine light (MIL) illuminated on dashboard
- Intermittent warning lights
- Erratic gauge readings
Estimated repair cost
Typical range in Australia (parts + labour)
$100 – $500 AUD
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.
Get a diagnosis for YOUR car
Code B1904 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.