B1C28: Left Thorax Squib 1, High

Circuit fault

What B1C28 means

The controller expects the thorax airbag firing loop to read within a tight resistance band. A value above the band means something in the path is adding resistance, which threatens the inflator's ability to fire on the current available during a side impact. That is enough for the controller to store B1C28 and disable the system.

High readings on a seat circuit usually trace back to the connector under the seat. It gets exposed to shoes, spilled drinks, salt, and vacuum cleaner attachments, and terminals in that environment corrode long before the wire itself gives up. Opening the connector and looking at the terminals answers the question faster than any meter reading taken from the other end of the harness.

Common causes

• Corroded terminals in the yellow connector beneath the seat
• A pin spread or partly backed out of the connector body
• A repair splice in the seat harness with a weak crimp
• Oxidation where the seat harness plugs into the floor harness
• An inflator in the seat back reading above its normal resistance

Crash data or hardware fault?

This is a live measurement, so B1C28 sits with the circuit codes and clears as soon as the resistance is back where it belongs. Crash data is the other category, written permanently the moment an airbag deploys and untouchable by any scan tool, which is why it requires a module level service.

Does our reset clear it?

Clearing or resetting the module does not reduce resistance in the seat airbag loop. The controller reads it again on the next key cycle and writes B1C28 once more. Clean or replace the connection, or replace the airbag if the inflator is out of spec. The mail-in reset we offer is for modules holding crash data or a stored internal fault.

Which makes throw it

Dodge is the make carrying B1C28 in our data, on the left side seat thorax airbag circuit.

What to do next

Separate the connector under the seat and inspect both halves for green or white corrosion on the terminals, because that is the leading cause of a high reading in this location. Measure the airbag on its own and then the harness back to the controller. Replace whichever side reads out of range, and reach us at 501-988-0611 for a genuine OEM seat airbag if that is the part. Related codes: B1C27, B1C29, 31-3X.