OBD-II trouble code
B00A1: Occupant Position System (Subfault)
The airbag/SRS control module detected a fault in the Occupant Position System, which senses how the front passenger is positioned so the airbag can deploy appropriately. 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 B00A1 mean?
B00A1 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 Position System.' Where the Occupant Classification System (B00A0) judges the size or presence of the front passenger, the Occupant Position System is concerned with where that occupant is — whether they are seated normally or 'out of position,' such as leaning forward, close to the dash, or off to one side. Some vehicles use position or proximity sensing as part of an advanced restraint system so the module can suppress or scale the passenger airbag when a normal deployment could injure an out-of-position occupant. It typically relies on seat-mounted sensors and shares the passenger seat's occupant-detection wiring, reporting to the main airbag control module.
The module sets B00A1 when the position system reports invalid data, loses communication with its sensor or sub-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 sensor, a mis-calibrated or un-zeroed system, or a faulty module. A symptom byte appended to the code narrows down the exact fault. Because the sensor and its wiring live in or 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 occupant-sensing designs vary widely and not every vehicle has a distinct position system.
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 calibration, and the fault should not be left unrepaired.
Common causes
- Corroded, backed-out, or loose connector in or under the passenger seat
- Failed occupant position/proximity sensor
- Damaged wiring in the seat harness from seat travel or floor moisture
- System out of calibration or never zeroed after seat/sensor service
- Faulty occupant-detection sub-module
- Aftermarket seat covers, heaters, or heavy items on the seat interfering with the sensor
Symptoms
- Airbag / SRS warning light on
- Passenger airbag on/off indicator stuck, blank, or reading incorrectly
- Stored B00A1 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 B00A1 with its full symptom byte and any companion occupant-detection codes such as B00A0.
- 2.Note whether the passenger airbag on/off indicator behaves correctly with the seat empty and with an adult seated in a normal position.
- 3.Confirm no aftermarket seat cover, seat heater, or heavy item 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 circuit and any sub-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 zero/recalibration procedure, which many systems require.
- 7.Repair the wiring/connector or replace the indicated sensor or 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 a recalibration can be inexpensive, while a failed occupant-sensing sensor or sub-module is much costlier and often needs calibration. SRS diagnostic time typically runs $100-$200; 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.