B1001: Diagnosis Sensor Unit Out of Order

Hardware fault

What B1001 means

Nissan calls the brain of the restraint system the air bag diagnosis sensor unit. It bolts under the center console, carries the impact sensors for frontal and side collisions, and holds a backup power supply so the system still works if the battery is torn loose in a collision. Every time the key goes to ON, that unit checks itself and the circuits it watches.

Nissan service data groups B1001 through B1005 under one heading with one detecting condition, that the diagnosis sensor unit is out of order, and one listed cause, an internal breakdown in the unit. Newer manuals print the same block under the name CONTROL UNIT. The number tells you which internal check failed, but Nissan does not publish what each one covers, so the code points at the unit rather than at a specific circuit.

Scope this reading to Nissan and Infiniti. On GM cars and trucks, B1001 is an option configuration error, where the sensing and diagnostic module and the body control module disagree about the VIN or the stored restraint ID. That one gets sorted out with programming.

Common causes

• An internal breakdown inside the diagnosis sensor unit, the only cause Nissan lists for this code
• A loose or corroded SRS connector at the unit under the center console
• Damaged wiring in the harness the unit monitors
• Supply voltage dropping or spiking while the unit runs its key-on self-check
• A control unit installed from another vehicle that arrived with its own stored faults

Crash data or hardware fault?

Hardware. B1001 is the unit reporting that it failed its own check, so there is no deployment record behind it. Nissan's diagnostic procedure walks a technician through the harness connector and the wiring first, then goes to replacing the unit if those check out. That order is worth following, because a poor connection at the console produces the same code as a dead unit.

Does our reset clear it?

It depends on what is actually wrong. If the unit failed internally, clearing memory will not fix it and the code comes back at the next key-on. If the unit is sound and B1001 was logged during a voltage event or a connection problem, our airbag module reset clears the stored fault once the underlying issue is repaired. Send the unit in and we test it first, so you find out which situation you are in before spending anything. When a unit is genuinely finished, you can search airbag control modules by year and model.

Which makes throw it

B1001 in this form belongs to Nissan and Infiniti, and it turns up across Altima, Sentra, Versa, Rogue, Juke, X-Trail, Qashqai, and the Infiniti G and Q cars. GM uses the same number for an SDM option configuration error, so a B1001 read on a Chevrolet, GMC, or Buick is a different repair entirely.

What to do next

Start with the checks Nissan puts first: battery condition, the power and ground feeds, and the connector under the console. Disconnect the battery and let the system sit at least three minutes before unplugging anything, so the backup supply bleeds down. If the connections are clean and the code holds, send us the unit for testing. Related codes from the same block: B1002, B1013, and B1015.

Related codes: B1002, B1013, B1015, B1000

Keep reading:

• Airbag module reset
• Airbag control module
• Nissan
• Infiniti

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.