B0091 is GM's code for the center front impact sensor. The sensing and diagnostic module powers that sensor, listens to it over a serial link, and stores B0091 when it stops reporting correctly. On trucks and SUVs from the late 2000s onward this is one of the more common airbag codes we get calls about, and corrosion is usually the reason.
GM mounts front impact sensors low in the front structure so they feel a hit before the passenger compartment does. The center front impact sensor sits near the middle of the lower radiator support area, ahead of the engine and behind the bumper. It reports to the SDM, and the SDM weighs what it hears from the front sensors against its own internal accelerometer before it commands anything to deploy.
GM appends a symptom byte to this code, and the byte does most of the diagnostic work for you. In GM service data, B0091 01 is a short to battery, 02 is a short to ground, 05 is a short to battery or an open circuit, 0F is erratic, 39 is an internal electronic failure inside the sensor, 3A is an incorrect component installed, and 71 is invalid serial data received. Write the byte down before anyone clears codes.
From there the byte sorts the job. 39 and 0F point at the sensor itself. 01, 02, and 05 point at the wiring between the sensor and the module. 3A means the part installed is not the part the SDM expects, which turns up after front end repair when a sensor from a different model got fitted.
Hardware. B0091 describes a sensor and its circuit, and it sets on vehicles that have never been in an accident. The corroded sensors on salt belt trucks are the clearest example.
The confusion comes from collision work. A front hit destroys these sensors, so B0091 shows up alongside a locked SDM on a large share of the trucks we see. The sensor is a parts and wiring repair. The locked module is its own job, and doing them out of order means doing the module twice.
No. The SDM is reporting a live problem with a sensor, so restoring its memory changes nothing and the code comes straight back on the next key cycle. Replace or repair the sensor and its circuit first.
If the airbags deployed and the module is holding crash data, that part is our work. Send the SDM in and our airbag module reset returns it to a clean state. Genuine OEM front impact sensors are searchable by vehicle in the parts store.
B0091 is GM, and it reads the same on Chevrolet, GMC, Cadillac, and Buick vehicles built with a center front sensor. Silverado, Sierra, Tahoe, Yukon, Suburban, Escalade, Avalanche, and the full size Express and Savana vans are where we see it most. Not every GM vehicle carries a center sensor, and on one that only has left and right front sensors the equivalent codes are B0083 and B0084 instead.
Read the code with its symptom byte, then get under the front of the vehicle. Unplug the sensor and look at both halves of the connector for corrosion and at the sensor housing for cracks. A split case on a salt belt truck ends the diagnosis right there. Follow the harness back along the radiator support for chafe damage while you are under there.
Replace the sensor with the correct part number for the vehicle, since a substitute from a similar model sets the incorrect component byte and puts the light straight back on. Related codes are B0083 and B0084 for the left and right front impact sensors and B0086 for the right front side impact sensor. If your year and model are not in the parts store, send us a part request.
Related codes: B0083, B0086, B0100
Keep reading:
Code scope: Chevrolet, GMC, Cadillac. The same number can mean something different on another manufacturer, so match the code to your make before you act on it.
A reset clears stored crash data. A replacement part fixes a hardware fault. We have read these codes since the nineties and will tell you which one you are looking at.
Genuine OEM, tested, and shipped ground from Jacksonville, Arkansas.
Chevrolet parts and codes · Do not see it listed? Request a part or call 501-988-0611.