OBD-II trouble code
B0050: Driver Seatbelt Sensor (Subfault)
The airbag/SRS control module detected a fault in the driver's seat belt sensor circuit — the sensor that tells the restraint system whether the driver is buckled. Airbag and pretensioner behavior may be affected, so this needs prompt professional attention.
Quick facts
- System
- Body
- Category
- Airbag / SRS Restraints
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $500
- DIY difficulty
- Shop recommended
What does B0050 mean?
B0050 is a body (B) code stored by the airbag/SRS control module — often called the Restraints Control Module (RCM) or, on General Motors vehicles, the SDM (Sensing and Diagnostic Module). Its SAE-generic definition is 'Driver Seatbelt Sensor,' referring to the switch or sensor that reports whether the driver's seat belt is buckled. That signal is not just for the seat-belt reminder chime: modern restraint systems use belt status to tailor how the airbag and seat-belt pretensioner behave in a crash, so the module watches this circuit closely.
The module sets B0050 when the driver seat belt sensor reports invalid data or its circuit falls out of specification — an open or short in the buckle wiring, a corroded or backed-out connector under the seat, a failed buckle switch, or an internal module fault. A symptom byte appended to the code (for example an open-circuit, short-to-ground, or short-to-power indicator) narrows down the exact condition. Because the buckle and its harness live at floor level and flex every time the seat moves, the most common trouble spots are the connector under the driver's seat and the section of wiring that bends with seat travel; spilled liquids, floor moisture, and aftermarket seat or seat-heater work are frequent contributors.
This is a supplemental restraint fault, not a driveability fault: the engine runs and the car drives normally. But with an SRS fault stored, the airbag warning light is on and the protection the system is designed to provide may not perform as intended — and airbag/pretensioner circuits carry a small risk of unintended deployment when mishandled. SRS diagnosis and repair should be left to a qualified technician who can safely disable the system, and the fault should not be ignored. Confirm the exact definition against your make's service data, since B-codes are applied differently across manufacturers.
Common causes
- Corroded, backed-out, or loose connector under the driver's seat
- Damaged buckle wiring where the harness flexes with seat travel
- Failed driver seat belt buckle switch/sensor
- Moisture intrusion or spilled liquid at the floor/under-seat connector
- Wiring damaged by aftermarket seat covers, seat heaters, or seat swaps
- Faulty airbag/SRS control module
Symptoms
- Airbag / SRS warning light on
- Seat-belt reminder chime or indicator behaving incorrectly
- Stored B0050 fault (often with a symptom byte) in the restraints module
- No effect on engine or driving performance
Diagnostic steps
- 1.Use a scan tool that can access the airbag/SRS module and record B0050 with its full symptom byte and any companion restraint codes.
- 2.Confirm the exact definition for the specific make and model, since B0050 is applied differently across manufacturers.
- 3.With the SRS safely disabled per the service procedure, inspect the connector under the driver's seat and the buckle harness for corrosion, moisture, or backed-out terminals.
- 4.Check the section of wiring that flexes with seat travel for chafing, pinching, or breaks.
- 5.Measure the buckle switch/sensor circuit against specification to separate a wiring or connector fault from a failed buckle.
- 6.If several belt-sensor codes are stored together, focus on a shared connector, power, or ground rather than multiple independent failures.
- 7.Repair the wiring/connector or replace the buckle switch, then clear codes and confirm the SRS light stays off.
Repair cost
$100 – $500
A connector or wiring repair can be modest, while a replacement driver seat belt buckle with its integrated sensor commonly runs $150-$400 including diagnosis. SRS diagnostic time typically runs $100-$200. Because this is airbag/SRS work, plan for professional diagnosis rather than a DIY guess.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with airbag / srs crash sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.