Code Definition

B0109 — Side impact module LHR deployment loop resistance below 1.3 Ohms

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

About B0109

B0109 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 B0109 is stored, the module has detected a signal or supply voltage lower than the expected operating range.

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 B0109 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

DTC B0109 sets when the airbag control module, also called the SRS ECU, measures the resistance of the left hand rear (LHR) side impact airbag deployment loop below the specified threshold of 1.3 ohms. The deployment loop carries the firing current to the side impact squib, and the module constantly monitors its resistance to confirm the airbag can be fired and to detect faults. A reading below 1.3 ohms points to a low resistance or short condition, typically the two squib wires touching, a short to ground, or contamination bridging the connector, rather than an open circuit. When B0109 is sto...

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