What Does B0042 Mean?
This code indicates a fault in the second stage deployment circuit for the left frontal airbag in the third row seating position. The Restraint Control Module (RCM) or Airbag Control Module has detected an abnormal condition in the deployment control circuit, specifically a subfault condition that affects the advanced deployment capability. This prevents proper multi-stage airbag deployment and compromises occupant protection in that seating position.
Safety Warning
This is a critical safety system fault that compromises airbag deployment capability in the third row left position during a collision. The vehicle should not be driven with occupants in that seating position until repaired, as the airbag may not deploy properly or at all in a crash.
Common Causes
35%
Faulty third row left seat-mounted side airbag or internal circuit resistance out of specification
30%
Damaged or corroded wiring harness and connectors between RCM and third row left airbag
20%
Faulty Restraint Control Module (RCM) with internal deployment driver circuit failure
10%
Incorrect airbag replacement or programming after previous repair causing compatibility issues
5%
Low vehicle battery voltage or poor ground connection affecting airbag system integrity monitoring
Diagnostic Steps
1
Step 1: Perform visual inspection of third row left seat area for physical damage, aftermarket modifications, or signs of previous airbag deployment. Check airbag connector under seat for corrosion, bent pins, or looseness.
2
Step 2: Measure airbag squib resistance at the airbag connector using a digital multimeter (DMM) with airbag disconnected and RCM powered down. Typical specification is 2-3 ohms; compare to vehicle-specific service manual values.
3
Step 3: Inspect airbag wiring harness from third row seat to RCM for chafing, pinching, water intrusion, or damage from seat mechanisms. Pay special attention to areas where harness routes through seat tracks and floor openings.
4
Step 4: Check RCM connector terminals for corrosion, pushed-back pins, or damage. Measure voltage supply to RCM (typically battery voltage) and verify proper ground circuits with less than 0.5 ohms resistance to chassis ground.
5
Step 5: Use advanced scan tool functions to perform airbag system component testing if available, checking deployment circuit continuity and resistance values through RCM self-test routines.
6
Step 6: If all circuits test normal, suspect RCM internal fault. Replace RCM with properly programmed unit, clear codes, and perform complete airbag system verification test to confirm all deployment circuits function correctly.
Estimated Repair Cost
$300 - $1,800
Parts + labor, varies by vehicle and location
This code indicates a fault in the second stage deployment circuit for the left frontal airbag in the third row seating position. The Restraint Control Module (RCM) or Airbag Control Module has detected an abnormal condition in the deployment control circuit, specifically a subfault condition that a...
The most common cause of B0042 (Third Row Left Frontal Stage 2 Deployment Control (Subfault)) is: Faulty third row left seat-mounted side airbag or internal circuit resistance out of specification
Typical repair costs for B0042 range from $300 to $1,800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This is a critical safety system fault that compromises airbag deployment capability in the third row left position during a collision. The vehicle should not be driven with occupants in that seating position until repaired, as the airbag may not deploy properly or at all in a crash.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B0042 to identify the root cause.
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Quick Info
Category
Body
System
Supplemental Restraint System (SRS/Airbag)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
