B1040 is one of four Nissan codes covering the crash zone sensor, the front impact sensor bolted to the radiator core support. The diagnosis sensor unit watches that sensor's lines with the key on, and B1040 is the shorted version of the fault. Nissan's own DTC index labels it SHORT and upper ground short.
The crash zone sensor is the main G sensor for frontal impacts. Nissan describes it as the sensor that generates a signal voltage when it detects deceleration beyond a specified level caused by a frontal collision. When the diagnosis sensor unit and its own safing sensor both read a level that exceeds the threshold, the driving circuit switches on and feeds the initiators for the front airbags and the seat belt pretensioners.
Because that sensor gets a vote in the deployment decision, the module monitors its lines for opens and shorts. Nissan groups the results under one heading with four numbers: B1035 for a communication failure, B1036 for an unmatched sensor, B1038 for the open and upper battery short condition, and B1040 for the short and upper ground short condition. B1033 and B1034 sit above them for a sensor that has failed internally.
The detecting condition Nissan prints for all four is one sentence: the crash zone sensor is out of order. The possible causes are disconnection of the wiring harness or an open or short in it, an internal breakdown in the crash zone sensor, or an internal breakdown in the diagnosis sensor unit.
Circuit fault, with a strong collision connection. The sensor mounts on the core support directly behind the bumper, so a front impact that never reached the cabin can still crush the sensor or pinch its wiring. That makes B1040 one of the more common codes on a Nissan coming out of front end repairs.
Nissan keeps the crash record itself on a different number. B1209, frontal collision detection, is what the module stores when the front airbags and pretensioners have deployed. B1040 and B1209 together tell you the vehicle took a real hit and the sensor circuit was damaged in it.
No. B1040 is a live measurement, and a reset does not change what the module reads on the sensor lines.
Nissan's repair order is the useful part. Repair or replace the wiring harness and connectors first, replace the crash zone sensor second, replace the diagnosis sensor unit last, and recheck the SRS at every replacement. We list genuine OEM impact sensors and airbag control modules for Nissan and Infiniti. If the airbags deployed and the module is holding the collision record, our airbag module reset clears it out of your original unit.
B1040 with this meaning is Nissan restraint system wording, and the same SRS section appears in Infiniti manuals of the same period, so Nissan and Infiniti vehicles share it. The 2009 Rogue manual quoted here prints B1035, B1036, B1038 and B1040 on a single chart under the crash zone sensor heading. Mounting position varies a little by model, but the core support location holds across the range.
Turn the ignition off, disconnect both battery terminals, and wait at least three minutes before touching anything in the system. Nissan calls that out specifically so the backup capacitor has time to discharge.
Then look at the front of the vehicle. Follow the harness from the diagnosis sensor unit forward to the sensor and check for a pinched, melted or crushed section, especially anywhere the loom passes a bracket edge. Check the connector for water and green film. If the harness and connector are good and the code stays, the sensor is next in Nissan's order and the module is after that. When the sensor is the part you need and it is not listed on our site, send us the number through our parts request form.
Related codes: B1038, B1035, 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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