B1004 is one of the Nissan and Infiniti control unit codes. The air bag diagnosis sensor unit reported an internal breakdown during its self-check. Where Nissan mounts that unit has a lot to do with why these codes show up on older cars.
Nissan bolts the diagnosis sensor unit to the floor under the center console. That location keeps it near the center of the vehicle for accurate crash sensing, and it also puts the electronics at the lowest point in the cabin. Anything that gets into the carpet eventually gets to the unit.
B1004 sits in the B1001 to B1005 block that Nissan documents as one item, with the detecting condition reading that the diagnosis sensor unit is out of order and an internal breakdown as the listed cause. The air bag lamp comes on or blinks, the system stops arming, and the unit stays flagged until it is repaired or replaced.
On a car with any history of a wet floorboard, B1004 and its neighbors deserve a close look before parts get ordered. Corrosion in a connector or on the board produces the same self-check failure as a genuinely dead unit.
Hardware. Nissan lists no crash condition for B1004. Collisions on these vehicles are recorded under the separate frontal and side collision detection codes, so a B1004 by itself points at the unit rather than at an accident. If the car has been in a collision, expect the collision codes stored alongside it, and treat those as their own line item.
Not on its own, if the unit truly failed internally. A reset restores stored memory to factory condition and clears crash records, and that does nothing for corroded pins or a dead board. Testing is the useful step. Send the unit to us and we test it, then tell you whether an airbag module reset will hold or whether you are better off with a replacement airbag control module for your year and model.
B1004 in this form is Nissan and Infiniti. It is common on Altima, Sentra, Versa, Note, Micra, Rogue, and Pathfinder, along with the Infiniti models sharing the same restraint electronics. Our guide on what an SRS airbag module is covers what this unit does in more depth.
Pull the console trim and look at the unit and its connector before spending anything. Dry, clean, and tight is what you want to see. Check the carpet padding underneath while you are in there, since a slow leak can soak the pad without ever showing on the surface. Fix the water source first, then deal with the electronics, or the new part goes the same way as the old one. If the unit is clean and the code stays, mail it to us for testing. Related codes: B1002, B1009, and B1015.
Related codes: B1002, B1009, B1015, B1000
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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