Code Definition

B0138 (72) — LHF seat belt pretensioner squib Circuit shorted to power

System: Body  |  Type: Generic (OBD-II Standard)  |  Make: Toyota

About B0138

B0138 is a generic (obd-ii standard) body diagnostic trouble code recorded for Toyota vehicles. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B0138 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

Because B0138 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The airbag control module, called the Center Airbag Sensor Assembly or SRS ECU on Toyota, continuously monitors the left hand front seat belt pretensioner squib circuit for correct resistance and bias voltage. DTC B0138 sub code 72 sets when the module detects one of the pretensioner squib wires shorted to a voltage source, that is an unintended low resistance path to battery or ignition positive. The pretensioner is a pyrotechnic device in the seat belt buckle or retractor that fires to pull slack out of the belt during a collision, and stray voltage on the firing line both corrupts the monit...

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