Damaged or pinched wiring harness under the driver seat, often from seat movement or cargo interference.; Failed occupant position sensor C itself, due to wear or internal electronic failure.; Corroded or loose electrical connector at the sensor or under the seat.; Faulty Occupant Classification Module (OCM) or its software, though less common.; Water intrusion or liquid spill into the seat cushion affecting the sensor or wiring.; Aftermarket seat covers or heavy objects on the seat that interfere with sensor calibration.

DTC codes / B00xx · Airbags, seats, doors, lights and comfort systems / B00B9

B00B9Driver Seat Occupant Position Sensor C

Q: What does code B00B9 mean?

Driver Seat Occupant Position Sensor C. B00B9 indicates a fault in the driver seat occupant position sensor C circuit, which is part of the Occupant Classification System (OCS) that determines whether the driver seat is occupied and how the occupant is positioned. The computer has detected an out-of-range signal, an open circuit, or a short circuit in the sensor's wiring or internal electronics, and it stores this code while disabling or altering the passenger airbag deployment strategy.

B00B9 indicates a fault in the driver seat occupant position sensor C circuit, which is part of the Occupant Classification System (OCS) that determines whether the driver seat is occupied and how the occupant is positioned. The computer has detected an out-of-range signal, an open circuit, or a short circuit in the sensor's wiring or internal electronics, and it stores this code while disabling or altering the passenger airbag deployment strategy.

SystemBody

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

The airbag warning light on the instrument cluster stays illuminated.
A message such as 'Service Airbag System' or 'Occupant Sensor Fault' appears on the driver information display.
The passenger airbag may be automatically disabled or its deployment may be altered, even though the fault is on the driver seat.
In some vehicles, the seatbelt reminder chime or warning may behave erratically.
Often no symptoms besides the warning light, with no noticeable change in vehicle operation.

Common causes, most likely first

Damaged or pinched wiring harness under the driver seat, often from seat movement or cargo interference.
Failed occupant position sensor C itself, due to wear or internal electronic failure.
Corroded or loose electrical connector at the sensor or under the seat.
Faulty Occupant Classification Module (OCM) or its software, though less common.
Water intrusion or liquid spill into the seat cushion affecting the sensor or wiring.
Aftermarket seat covers or heavy objects on the seat that interfere with sensor calibration.

How to diagnose and fix it

Inspect the under-seat wiring harness and connectors for damage, corrosion, or looseness, and repair as needed.
Check for any aftermarket accessories or objects that may interfere with the sensor and remove them.
Use a scan tool to read live data from the occupant position sensor and compare it to expected values through the seat travel.
Perform a resistance and voltage drop test on the sensor circuit to identify opens or shorts.
If the sensor signal is erratic or out of range, replace the occupant position sensor C following the manufacturer's procedure.
After repair, clear the codes and perform the required occupant classification system calibration or relearn procedure with a scan tool.
Verify the repair by confirming the airbag warning light is off and no codes return after a test drive.

Occupant sensor faults often misdiagnosed

A common oversight is replacing the sensor when the real problem is a chafed wire under the seat that only loses connection when the seat is moved.
The driver seat occupant position sensor C is sometimes part of a bladder or strain gauge system that requires calibration after any seat repair, and skipping this step will set the code again.
This code can be set by a weak battery or low voltage during cranking, so always check the battery and charging system before condemning the sensor.
On some vehicles, the occupant classification system uses the same wiring as the seat heater, and a short in the heater circuit can mimic a sensor failure.
The code does not always mean the sensor is dead; it can also be triggered by a faulty seat position memory module or a misadjusted seat track sensor.

Can I keep driving with B00B9?

You can generally continue driving, but the airbag system may be partially disabled, reducing occupant protection in a crash. Avoid carrying a passenger in the affected seat until the fault is repaired, and have the system diagnosed promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.