B1086 is Nissan's code for an open circuit in the left front seat belt pretensioner. The air bag diagnosis sensor unit measures that firing loop, reads it as open, and turns on the air bag warning light. On a car with collision history the reason is usually straightforward, because a pretensioner that has already fired reads open.
Nissan and Infiniti call the airbag module the air bag diagnosis sensor unit, and on most models it is bolted to the floor under the center console. A seat belt pretensioner is a small pyrotechnic device built into the retractor or the buckle that pulls the slack out of the belt in the first fraction of a second of a crash. It has an igniter, and the module treats that igniter as one more firing loop to measure at every key on.
B1086 is the open circuit member of a small group. B1087 is the same left circuit shorted to a power supply, and Nissan carries further numbers for shorts to ground. The right side has its own number, published as B1081 on some models and B1084 on others, so check the chart for the vehicle in front of you rather than assuming the pair.
Nissan's own diagnosis order for this code is short and worth following in sequence. Read the self diagnosis result, check the harness connector, check the wiring harness, replace the pretensioner, and only then replace the diagnosis sensor unit.
It depends on the car, and this code is one of the few where both answers are common. On a vehicle with no collision history B1086 is a circuit fault, and the connector under the sill is usually where it ends.
On a vehicle that has been hit, the belt fired, the pretensioner is spent, and the module is almost certainly holding B1209 frontal collision detection as well. That second code is stored crash data and no scan tool clears it.
Not by itself. The pretensioner is hardware, and restoring the module's memory does not rebuild it. What we can do is both halves of the job.
Send us the belt and we rebuild the retractor and pretensioner back to a working assembly through our seat belt repair service, which covers pretensioner repair on single and dual stage belts. Send the module and our airbag module reset clears the stored collision record. Order matters here. Get the belt and any deployed airbags back in the car first, then bring the module back to a clean state.
B1086 in this form is Nissan and Infiniti, which share the diagnosis sensor unit and the code chart. It turns up on Altima, Sentra, Versa, Rogue, Juke, Frontier, Titan, Pathfinder, and NV200, on the Infiniti models built alongside them, and on the Micra and X-Trail in markets that get them. Other manufacturers use B1086 for their own circuits, so confirm the code came from a Nissan module before acting on any of this.
Pull the lower B-pillar trim on the left side and get to the connector at the bottom of the belt assembly. Disconnect the battery and wait out the discharge time before touching it. Reseat the connector, look at the pins, and check the harness where it enters the sill. If the belt or the seat has been out of the car for carpet or interior work, that connector is the first suspect.
If the belt fired, the assembly has to be rebuilt or replaced before the code will clear. We rebuild seat belts and we stock replacement pretensioner assemblies. Related codes are B1087 for the same circuit shorted to power and B1081 for the right front pretensioner. If you are not sure which kind of belt your car has, our guide on single stage versus dual stage belts covers how to tell them apart.
Related codes: B1087, B1081, B1209
Keep reading:
Code scope: Nissan, Infiniti. 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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