OBD-II code B0042 indicates a malfunction in the deployment control circuit for the second-stage frontal airbag at the third-row left seating position. The airbag control module has detected an out-of-range resistance, open circuit, or short in the inflator circuit, which disables that stage of airbag deployment. The airbag/SRS warning light will typically be illuminated, and the affected airbag may not deploy in a crash.
The deployment component itself is the most common failure point. Internal resistance drift, open filaments, or a shorted squib are well-documented failure modes, particularly as the airbag ages.
Wiring routed under the third-row carpet, behind trim panels, or along the floor pan can be pinched, chafed, or stressed by seat movement. Water intrusion and rodent damage are also common in this area.
The yellow SRS connector at the airbag module is sensitive to terminal corrosion, partial engagement, or backed-out pins, all of which push circuit resistance outside the module's acceptable range.
If the airbag or related wiring was disturbed during a previous repair or seat removal, a missing or misinstalled connector can leave the circuit fault active.
Less common, but the airbag control module itself can develop internal faults that incorrectly flag this circuit. It is a plausible but infrequent cause, and should be confirmed only after the wiring and squib have been ruled out.
This is not a PCM-controlled code. Replacing the engine computer will not fix B0042 and is an incorrect repair; the SRS module handles this circuit.
No. The third-row left stage 2 frontal airbag may not deploy properly in a crash, reducing protection for that occupant. The fault should be repaired promptly. Other restraints in the vehicle typically remain functional, but a deployed third-row airbag that fails to fire is a real safety loss.
No. B0042 is a body/SRS code, not a powertrain code. The engine computer does not control airbag deployment, and replacing it will not clear the fault. This repair is commonly suggested by people unfamiliar with body codes, but it is incorrect; the SRS module, wiring, and inflator are what need to be diagnosed.
The code can often be cleared, but if the underlying electrical fault is still present, it will return on the next ignition cycle or self-test. Clearing the code is not a repair and should only be done after the fault has been fixed and verified.
Yes, the part itself can be sourced and installed by a qualified technician or vehicle owner, but SRS service carries real risk of accidental deployment and injury. The manufacturer's procedures for battery isolation, capacitor discharge, and torque specifications should be followed exactly, and the system should be verified with a scan tool after the repair.