OBD-II trouble code
B00A0: Occupant Classification System (Subfault)
The airbag/SRS control module detected a fault in the Occupant Classification System, which decides whether the front passenger airbag should be enabled. Passenger airbag operation 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 – $900
- DIY difficulty
- Shop recommended
What does B00A0 mean?
B00A0 is a body (B) code stored by the airbag control module. It is a hexadecimal code — the character after B00 is the letter A, not a number — and its SAE-generic definition is 'Occupant Classification System.' The Occupant Classification System (OCS), sometimes called the passenger presence or occupant detection system, is the part of the supplemental restraint system that judges who is in the front passenger seat: an adult, a smaller occupant, a child in a seat, or an empty seat. It usually uses a weight-sensing mat or bladder and sometimes a seat-belt tension sensor mounted in or under the passenger seat, feeding an OCS module that reports its classification to the main airbag control module. That classification drives the 'passenger airbag on/off' indicator and lets the module suppress or scale the passenger airbag to protect a child or small occupant.
The module sets B00A0 when the OCS reports invalid data, loses communication with the classification module, or the sensor circuit is out of specification — an open or short in the sensor wiring, a corroded or backed-out connector under the seat, a failed weight sensor or bladder, a mis-calibrated or un-zeroed system, or a faulty OCS module. A symptom byte appended to the code narrows down the exact fault. Because the sensor and its wiring live under the passenger seat, connectors disturbed by seat travel, floor moisture, spilled liquids, or aftermarket seat-cover and floor-mat work are common trouble spots, and some systems require a zero/recalibration procedure after any seat or sensor service. Confirm the exact configuration against your make's service data, as OCS designs vary widely.
This is a supplemental restraint fault, not a driveability fault: the vehicle drives normally, but the passenger airbag may not enable, disable, or scale as designed, and airbag circuits carry a small risk of unintended deployment when mishandled. SRS diagnosis and repair should be performed by a qualified technician who can safely disable the system and run any required OCS calibration, and the fault should not be left unrepaired.
Common causes
- Corroded, backed-out, or loose connector under the passenger seat
- Failed occupant weight sensor, bladder, or seat-belt tension sensor
- Damaged wiring in the seat harness from seat travel or floor moisture
- OCS system out of calibration or never zeroed after seat/sensor service
- Faulty Occupant Classification module
- Aftermarket seat covers, heaters, or heavy floor mats interfering with the sensor
Symptoms
- Airbag / SRS warning light on
- Passenger airbag on/off indicator stuck, blank, or reading incorrectly
- Stored B00A0 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 B00A0 with its full symptom byte and any companion occupant-detection codes.
- 2.Note whether the passenger airbag on/off indicator behaves correctly with the seat empty and with an adult seated.
- 3.Confirm no aftermarket seat cover, seat heater, or heavy mat is interfering with the sensor, and remove anything unusual on the seat before testing.
- 4.With the system safely disabled per service procedure, inspect the under-seat connector and seat harness for corrosion, moisture, or backed-out terminals.
- 5.Check the sensor's circuit and the OCS module communication against specification to separate a wiring/connector fault from a failed sensor or module.
- 6.If the seat, sensor, or module was recently serviced, run the make-specific OCS zero/recalibration procedure, which many systems require.
- 7.Repair the wiring/connector or replace the indicated sensor or OCS module, recalibrate, then clear codes and confirm the SRS light stays off and the indicator reads correctly.
Repair cost
$100 – $900
A connector repair or an OCS recalibration can be inexpensive, while a weight sensor/bladder or the OCS module itself is much costlier and often needs calibration. SRS diagnostic time typically runs $100-$200; occupant weight sensor or module replacement with the required calibration commonly falls in the several-hundred-dollar range. SRS work should be done by a qualified technician.
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.