On GM vehicles from about 2007 forward, B0086 reports a problem with the right front side impact sensor. GM's own documentation says what happens when it sets: the airbag light comes on and the SIR system is disabled, with no deployments allowed. That makes it different from a deployment loop code, where the module will still try to fire.
GM's service data is clear that impact sensors are not part of the deployment loops. They are electronic units that feed information to the sensing and diagnostic module, which uses their input to judge the severity of a frontal or side collision and decide what to fire. B0086 covers the right front position, with B0085 for the left front, B0087 for the left rear, and B0088 for the right rear on vehicles that have them.
The symptom byte tells you the nature of the failure and each one leads somewhere different. GM lists 39 for an internal electronic failure in the sensor, 3A for an incorrect component installed, 71 for invalid serial data, 0F for erratic messages, and 00 or 02 and 05 depending on platform for the open and shorted circuit conditions.
The module gives the sensor a chance before it gives up. It resets the sensor up to two times by cutting and restoring power. Only if the fault is still there after that does the code get stored, along with the conditions GM lists for setting it, which include no message received for more than 375 milliseconds and sensor current above 23 milliamps.
Hardware. The module is reporting that a physical sensor is failing, missing, or answering with the wrong identity. Nothing here is stored crash information. The practical consequence is bigger than with a loop code though, since GM disables deployments while this fault is active. A vehicle driving around with B0086 set has no side impact protection on that side.
No. A module reset clears stored data, and this code is a live report about a component. Replace the sensor with the correct GM part for the VIN, since symptom byte 3A exists specifically because the module compares the sensor's ID against what it has in memory. Genuine OEM impact sensors are in the parts store. If the vehicle deployed and the module locked, the module still needs an airbag module reset after the sensor is replaced.
The right front side impact sensor definition comes from GM service information for Chevrolet, GMC, Buick, and Cadillac vehicles built from roughly 2007 onward, and it is documented on both the full size trucks and the crossovers. Some older GM SIR references assign this number to a different circuit, so on an early 2000s vehicle look the code up against that model's own service data. Other manufacturers use B0086 for their own systems.
Read the symptom byte first, because it splits the job cleanly. A 39 sends you to the sensor. A 3A sends you to the part number, and it is worth confirming against the VIN, since sensors that look identical across a model line are frequently not interchangeable. The circuit codes send you to the two wire harness and its connectors.
If B0078, B0085, or a roof rail code is stored with it, check the shared harness and the module connector before condemning multiple sensors.
Related codes: B0077, B0078, B0083
Keep reading:
Code scope: Chevrolet, GMC, Cadillac, Buick. 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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