OBD-II trouble code
B0091: Left Side Restraints Sensor 1 (Subfault)
The airbag/SRS control module detected a fault in the left-side restraints sensor 1 circuit. Side-impact protection on that side may not deploy as designed, 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 – $700
- DIY difficulty
- Shop recommended
What does B0091 mean?
B0091 is a body (B) code stored by the airbag control module. Its SAE-generic definition is 'Left Side Restraints Sensor 1,' referring to one of the left-side satellite impact sensors that tell the module a side collision is occurring so it can fire the side and curtain airbags and seat-belt pretensioners on that side. The numbering (Sensor 1, 2, 3) distinguishes multiple side sensors: B0091 is Sensor 1, while B0092 covers Sensor 2 and B0093 covers Sensor 3 on vehicles that use them. As with all B-codes, the exact application varies by manufacturer, so confirm the definition against your make's service data.
The module sets B0091 when that sensor's circuit reads out of range — open, shorted, or with resistance outside the narrow band these safety circuits demand — or when the sensor stops reporting valid data. Because a side-impact sensor is mounted low in a door, B-pillar, rocker, or seat frame, its wiring and connector are exposed to moisture, road spray, and repeated flexing, which is why connector corrosion and harness damage are among the most common causes.
This is a supplemental restraint fault, not a driveability fault: the vehicle drives normally, but the side-impact protection on the affected side may not work as designed in a crash, 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 the fault should not be left unrepaired.
Common causes
- Corroded, wet, or loose connector at the side-impact sensor
- Damaged wiring in the door, rocker, or seat harness (flex fatigue or water intrusion)
- Failed left side-impact restraint sensor
- Prior collision or door/rocker repair that disturbed the sensor or wiring
- Restraint sensor replaced but not the correct part, or not properly seated
- Faulty airbag/SRS control module
Symptoms
- Airbag / SRS warning light on
- Stored B0091 fault in the restraints module
- No effect on engine or driving performance
- Possible additional side-restraint or occupant-sensing codes stored alongside it
Diagnostic steps
- 1.Use a scan tool that can access the airbag/SRS module and record B0091 and any companion restraint codes.
- 2.Confirm the exact definition for the specific make and model, since side restraint-sensor numbering differs across manufacturers.
- 3.With the system safely disabled per service procedure, inspect the left-side sensor connector and harness for corrosion, moisture, or damage.
- 4.Check areas exposed to water and flexing — the lower door, rocker, B-pillar base, or seat frame — where side-impact sensors live.
- 5.Measure the sensor circuit's resistance against specification to separate a wiring fault from a failed sensor.
- 6.If a sensor was recently replaced, verify it is the correct part and is fully seated (mounting affects the signal).
- 7.Repair wiring/connector faults or replace the indicated sensor, then clear codes and confirm the SRS light stays off.
Repair cost
$100 – $700
A connector or wiring repair can be modest, while replacing a side-impact restraint sensor commonly runs $200-$600 including diagnosis. Costs rise if the sensor is buried in a door or seat structure, or if the airbag/SRS control module itself is at fault. SRS work should be done by a qualified technician, so plan for professional diagnostic time.
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.