B220C: Controller Accelerometer Fault

Hardware fault

What B220C means

Every restraint controller carries its own accelerometer. Satellite sensors out at the body give it an early look at a side or frontal hit, and the internal accelerometer confirms what the vehicle is actually doing before the controller commits to firing anything. B220C says that internal sensor failed its self test, so the confirmation the controller depends on is missing.

There is no external wiring to chase on this one. The accelerometer is part of the controller assembly, sealed inside the housing. That makes the diagnosis short and the repair path narrow. Anything that stresses the controller, including water, impact, or a long history of low system voltage, can be what pushed the internal sensor into faulting.

Common causes

• A failed accelerometer inside the occupant restraint controller
• Water reaching the controller at its mounting location
• Physical shock to the controller, including being dropped during a repair
• Low or unstable system voltage over time
• A used controller installed with the fault already stored

Crash data or hardware fault?

This is a hardware fault, so it describes the controller's own condition rather than a measurement on a wire. Crash data is the other thing a controller stores, written once at deployment and permanent until reset. Both can be present in the same unit, and the reset only addresses the stored side.

Does our reset clear it?

Our reset returns the controller to factory condition, so B220C clears if it was stored rather than actively failing. If the accelerometer is truly bad, the controller reports it again as soon as it powers up. Sending the unit in is a reasonable way to find out which of those two you have, and we will tell you what the module does on the bench.

Which makes throw it

Jeep reports B220C on the occupant restraint controller. Accelerometer faults on other makes carry different numbers but describe the same internal part.

What to do next

Confirm the basics on the vehicle before you assume the controller is scrap: battery condition, charging voltage, ground connections, and any evidence of water where the unit is mounted. Once those are clean, the controller is the part in question. Mail it to us and we will reset it and let you know whether the internal fault stays. Related codes: B2209, B2722, B1019.