B0087 is the sensing and diagnostic module reporting that the left rear side impact sensor is not answering the way it should. GM's service data spells out the consequence: the SDM asks the instrument panel cluster to light the AIR BAG indicator, the SIR system is disabled, and no deployments are allowed. A vehicle driving with B0087 active has no airbag deployment available anywhere in the system.
GM's impact sensors are electronic units that report to the SDM over their own circuit, described in service information as equipment that supplements SIR system performance rather than parts of a deployment loop. Their job is to give the module enough information to judge how severe a collision is. B0087 covers the left rear position, B0088 the right rear, and B0085 and B0086 the two front side positions.
The set conditions are numeric. The code runs with ignition voltage between 9 and 16 volts. It sets when sensor current exceeds 23 milliamps for more than 5 milliseconds, or when the SDM has gone more than 375 milliseconds without a message from the sensor, along with the short, open, and identity conditions each carried by its own symptom byte.
Those bytes are the shortcut through the job. GM publishes descriptors for 01 short to battery, 02 short to ground, 04 open circuit, 05 high voltage or open, 0C low current, 39 internal failure, 3A incorrect component installed, and 71 invalid serial data. A 39 condemns the sensor, a 3A says the part in the car is not the one the module expects, and the remaining bytes point at the harness.
Hardware. The SDM is reporting on a physical component and its circuit as it reads them right now, and no collision record lives inside B0087.
What makes it consequential after a collision is the shutdown. With the SIR system disabled the module fires nothing at all, so a repaired vehicle still holding B0087 is not finished. GM also notes that a history version of the code clears itself once 100 malfunction free ignition cycles have passed, which is why a fault repaired weeks ago still shows on a scan.
No. Our reset restores modules holding locked crash data, and B0087 is a live hardware report. Repair the wiring or install the correct sensor and the code stops setting.
Genuine OEM impact sensors are searchable by vehicle in the parts store, and matching the part number to the VIN matters here, because GM built symptom byte 3A specifically to catch the wrong sensor. If the vehicle also deployed and the SDM locked with crash data, that half is our work: an airbag module reset returns your original module clear, and belts that locked go through seat belt repair.
B0087 as the left rear side impact sensor comes from GM service information and applies across Chevrolet, GMC, Buick, and Cadillac vehicles that carry rear side impact sensors, roughly 2007 onward. GM documents the B0083 through B0088 sensor block on cars, crossovers, and full size trucks, and publishes a combined B0086 or B0087 diagnostic on some platforms. Sensor position and mounting vary by body style, so use the service data for that model to locate it.
Get the symptom byte before anything comes apart, because it decides whether this is a wiring job or a parts job. Then look at the harness in the left rear door opening, since that run flexes every time the door is used. Check the connector terminals for spread contacts while the panel is off.
Read the rest of the memory as well. B0086 is the right front side sensor and B0083 is the left front impact sensor, and more than one sensor code at once usually points at a shared harness or a module connector rather than several failed sensors.
Related codes: B0085, B0086, B0088, B0083
Keep reading:
Code scope: Chevrolet, GMC, Buick, 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.
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