B1B55: Passenger Belt Sensor, High

Circuit fault

What B1B55 means

A buckle switch circuit has two normal values, one for latched and one for unlatched, and both sit well inside a known range. B1B55 sets when the reading climbs above that range. The most common electrical reason is the signal wire touching a source of voltage somewhere in its run, though a failed switch can produce the same result.

Since the controller cannot tell whether the passenger belt is fastened, it treats the input as invalid. The belt reminder may behave oddly and the airbag warning lamp stays lit, because the restraint system does not operate on a sensor value it knows is wrong.

Common causes

• The buckle signal wire chafed against a powered circuit under the seat or carpet
• A failed buckle switch that has gone open or is stuck in an out of range state
• Corrosion inside the under seat connector raising resistance on the return path
• An aftermarket seat heater, subwoofer, or alarm install tapped into the wrong wire
• A damaged pin at the controller connector losing its ground reference

Crash data or hardware fault?

B1B55 is a live circuit reading rather than a crash record. It reflects the voltage on the belt sensor line at this moment and clears when that line reads normal again. Stored crash data is fixed. It is written at the time airbags deploy and no scan tool or clearing routine removes it from the module.

Does our reset clear it?

Sending the module in for a reset does not change a high reading on this circuit. The fault is out in the vehicle, so the controller finds it again immediately. Track down the short to voltage or replace the buckle, and the code stops returning. The mail-in reset is for modules that hold deployment data or a stored internal fault, not for live wiring problems.

Which makes throw it

Our lookup shows B1B55 on Chrysler vehicles, matched to the first row passenger belt sensor circuit.

What to do next

Check for recent work under the passenger seat first, because a seat heater or audio install tapped into an SRS wire is a common source of a high reading. Unplug the buckle and measure the circuit at the connector to see whether the voltage is coming from the vehicle side or the switch side. That one test decides whether you are chasing wiring or replacing the buckle assembly. Related codes: B1B54, B1B56, B1140.