B1B12: Driver Knee Bolster Squib, Open

Circuit fault

What B1B12 means

A knee bolster airbag sits low under the steering column and deploys downward to keep the driver's legs and hips positioned in a frontal crash. Its inflator has a firing circuit the controller monitors the same way it monitors the steering wheel airbag. An open reading means that path is broken somewhere between the module and the inflator.

The location works against this circuit. Everything under the driver's knees gets kicked, bumped with cleaning equipment, and disturbed whenever someone works on the dash, the pedals, or the lower column covers. An airbag light that appears right after under dash work usually leads back to a connector that was never plugged in again, so the repair history is worth asking about first.

Common causes

• The knee airbag connector unplugged after lower dash or column work
• A wire broken behind the lower trim panel from repeated contact
• A terminal backed out of the connector body so it never makes contact
• An inflator that has failed open internally
• Harness damage from pedal, hood release, or under dash accessory work

Crash data or hardware fault?

As a circuit code, B1B12 reports what the controller measures live, and it reads normal again the moment continuity is restored. Crash data is a permanent record instead. It is written into module memory when the restraints deploy, and no scan tool or code clear function removes it.

Does our reset clear it?

Sending the module in for a reset will not close an open knee bolster circuit. The controller tests the loop again at startup and stores B1B12 a second time. Repair the connector or the wiring, or replace the knee airbag, before clearing anything. Our mail-in reset is meant for modules holding crash data or a stored internal hardware fault.

Which makes throw it

Chrysler, Dodge, Jeep, and Ram all use B1B12 with this meaning across vehicles sharing the occupant restraint controller.

What to do next

Drop the lower dash trim on the driver side with the battery disconnected and the system bled down, then confirm the knee airbag connector is seated and latched. An unplugged connector after other under dash work is the most common find. If it is connected, check continuity from the controller through to the inflator, and we can supply a genuine OEM knee airbag if the unit reads open. Related codes: B1B0A, B1B33, B1B07.