B1C27: Left Thorax Squib 1, Low

Circuit fault

What B1C27 means

Seat mounted thorax airbags deploy out of the seat bolster toward the door. Their firing circuit runs from the restraint controller, along the floor, and up into the seat frame. The controller tests that loop the same way it tests any inflator circuit, and B1C27 is stored when the resistance falls under the allowed range.

A seat mounted device puts its wiring in motion every time the seat is adjusted. Fore and aft travel, recline, and on some vehicles power adjusters all flex the harness, and that repeated movement is why side airbag circuits fail more often than the ones bolted to the dash.

Common causes

• Seat harness insulation worn through at a flex point under the seat
• The side airbag connector under the seat not fully latched
• Wiring crushed between the seat track and the floor pan
• An inflator shorted internally in the seat back airbag
• Corrosion in the connector from floor moisture or a spill

Crash data or hardware fault?

B1C27 belongs to the circuit family, which means it follows a resistance the controller reads continuously and clears when that reading returns to range. Crash data is a permanent record written at deployment, and no scan tool clears it, which is why a deployed module needs bench work instead of wiring work.

Does our reset clear it?

A reset does not repair a low side airbag circuit. The controller measures the loop again at the next startup and stores B1C27 back into memory. Repair the seat harness or replace the airbag first. If the vehicle deployed in a side impact and the module is carrying crash data behind this code, our mail-in reset is what clears that record.

Which makes throw it

Dodge and Jeep both use B1C27 in our lookup, on the left side seat thorax airbag circuit.

What to do next

Run the seat through its full range and watch the harness where it passes the track, since worn insulation at that point is the usual cause on seat mounted airbags. Check the yellow connector under the seat for full engagement. Measure the loop at the connector and at the controller to separate a harness short from a shorted inflator, and we can source a genuine OEM seat airbag if the unit has failed. Related codes: B1BC7, B1C28, B1023.