Code Definition

B0042 — LHF seatbelt deployment loop Circuit malfunction

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

About B0042

B0042 is a generic (obd-ii standard) body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B0042 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

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 B0042 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 (ACM) continuously monitors the Left Hand Front (LHF) seatbelt pretensioner deployment loop by passing a small diagnostic current through the circuit and measuring its resistance. DTC B0042 sets when the ACM detects an open circuit, a short to ground, or a short to voltage in this loop, causing the measured resistance to fall outside the programmed window. The pretensioner is a pyrotechnic device that pulls the seatbelt tight and locks it at the instant of a collision, so the ACM must confirm the firing circuit is electrically healthy at all times. When this code is s...

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