What it means
B0042 indicates the SRS/airbag control module has detected abnormally low resistance in the driver’s frontal airbag Stage-2 deployment loop (dual-stage inflators use Stage-2 for higher-severity impacts). OEM service information documents B0042 as “driver frontal deployment circuit (stage 2), resistance low,” with explicit thresholds on some platforms. For example, Saab WIS specifies that B0042 sets when the measured loop resistance is <≈1.5 Ω for ~2 s; GM criteria for similar systems note <≈1.3 Ω for ~500 ms triggers the low-resistance fault. JustAnswer+3Saab Wisonline+3Saab Wisonline+3
Typical symptoms
- AIRBAG/SRS warning lamp on, DTC stored; the module will inhibit that deployment loop until the fault is corrected and cleared. No engine drivability effect. Saab Wisonline
Severity / priority
High (safety-critical). Low resistance (often due to shorts) can prevent proper airbag deployment logic or cause unintended fault states; repair promptly and verify with a scan-tool check. Saab Wisonline
Common causes
- Short-to-ground/short-to-voltage or otherwise low-ohmic path in the steering-wheel airbag Stage-2 high/low control circuits. Saab Wisonline
- Clock-spring (spiral cable) damage in the steering column creating an unintended low-resistance path. TrailVoy
- Connector/terminal issues (backed-out pins, poor tension, corrosion, shorting-bar faults) at the wheel module, column, or intermediate harnesses. MyAirbags Blog
- Less common: driver airbag module (Stage-2 inflator) internal fault or SRS control module (SDM/RCM) fault. MyAirbags Blog
Diagnostic notes
- Use an SRS-capable scan tool to confirm B0042, capture freeze-frame, and check for companion Stage-2 codes (e.g., B0043 voltage out-of-range, B0044 open/high resistance) and Stage-1 loop codes (B0022/B0024/B0026). Follow OEM SRS safety procedures (battery disconnect/wait time; never probe live inflator circuits). Saab Wisonline
- Perform a visual/physical inspection of the clock-spring and steering-column/IP harness; flex harnesses while monitoring to expose intermittents. TrailVoy
- With the inflator safely disconnected per OEM, measure loop/segment resistance and compare to OEM thresholds (Saab ~<1.5 Ω/2 s; GM ~<1.3 Ω/0.5 s). Use the service-manual decision tree to distinguish short-to-GND/B+ vs. internal module issues. Saab Wisonline+2Charm+2
Possible fixes
- Repair wiring where a short/low-resistance condition is found; restore insulation, routing, and strain relief. Saab Wisonline
- Replace a failed clock-spring and perform any required initialization/calibration. TrailVoy
- Correct connector/terminal faults (retension pins, clean corrosion, replace terminals/housings; address shorting-bar issues). MyAirbags Blog
- Replace the driver airbag module (Stage-2) only if it fails OEM-directed tests; evaluate SDM/RCM last, after the loop hardware is proven good. Then clear DTCs, cycle ignition, and re-scan to verify. Saab Wisonline
Sources
- Saab WIS: B0042 (driver frontal Stage-2, resistance low) with numeric thresholds/timing; companion criteria for B0043/B0044. Saab Wisonline
- GM/chevy service criteria (summarized in technician references): low-resistance trigger around <~1.3 Ω for 500 ms for Stage-1/Stage-2 loops. Charm+1
- GM/aftermarket lists and practitioner notes confirming B0042 mapping to LF/driver Stage-2 resistance low and common harness/clock-spring issues. MyAirbags Blog+1