What does it mean?
B1879 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Driver-Side Pre-Tensioner Seat Belt Circuit Short To Body Ground .
Symptoms
- Air bag warning lamp on and the restraint system reports itself as unavailable
- Driver pretensioner disabled, so the belt will not be tensioned in an impact
- Fault often becomes permanent after a wet floor, a leaking door seal or a spilled drink
- Code may set again a few days after clearing if moisture is trapped in the connector
- No engine driveability symptoms, the complaint is purely a safety warning
Likely causes
- Firing wire chafed against a seat frame edge, seat rail or floor bracket until the insulation is worn through
- Harness pinched between the seat foot and the floor pan when the seat was refitted
- Corrosion or standing water in the under seat connector connecting a firing pin to the shield or to bare metal
- Damaged shorting bar in the connector that stays closed with the connector mated
- Internal short to the pretensioner housing inside the belt assembly
- Restraint control module ground side driver failure
How to fix it
- Apply air bag safety procedure first: ignition off, battery disconnected, stand time observed
- Read and record the codes with freeze frame, then check the carpet under both front seats for moisture
- Disconnect the pretensioner and measure resistance from each harness wire to a clean body ground; a low reading confirms the short
- Follow the harness along the seat frame and rails and inspect every point where it touches sheet metal or a bracket edge
- Dry and inspect the under seat connector, checking that the shorting bar releases correctly when the connector is mated
- Cure the source of the water, such as a door membrane, sunroof drain or windscreen seal, before repairing the wiring
- If the short remains with the harness disconnected at both ends, replace the seat belt assembly, and only then look at the control module