Damaged, loose or corroded connector at the third-row left restraint or its harness plug; Wiring fault such as an open circuit, short to ground or short to voltage in the deployment circuit, often from seat movement, trim removal or cargo damage; Faulty restraint device or its initiator in the third-row left position; Poor connection at the seat or trim-panel connector after seat folding, removal or refitting; Previous collision or water ingress damaging the harness or connectors; Faulty airbag control unit.

B0042

Third Row Left Frontal Stage 2 Deployment Control.

Generic
Body
Generic code
High severity

How this code is built

B: SystemBody
0: Defined bySAE, the same on every car
0: AreaBody area 0
42: FaultThe specific fault in that area

What it means

B0042 is defined here as a fault in the Third Row Left Frontal Stage 2 Deployment Control circuit of the supplemental restraint system. The airbag control unit monitors the deployment circuits for this position and set the code because it saw a resistance, voltage or communication reading outside the expected range. It only applies to vehicles fitted with third-row restraints, and the exact location and layout depend on the model.

Symptoms

Airbag or SRS warning light on the dashboard
Airbag light staying on after start-up instead of going out
Third-row left restraint may not deploy in a collision
Seat belt pretensioner or restraint warning message on some models
Other stored airbag or seat occupancy fault codes alongside B0042

Possible causes

Damaged, loose or corroded connector at the third-row left restraint or its harness pluglikely
Wiring fault such as an open circuit, short to ground or short to voltage in the deployment circuit, often from seat movement, trim removal or cargo damagelikely
Faulty restraint device or its initiator in the third-row left positionpossible
Poor connection at the seat or trim-panel connector after seat folding, removal or refittingpossible
Previous collision or water ingress damaging the harness or connectorspossible
Faulty airbag control unitrare

How to diagnose

Read all stored and pending codes and any freeze frame data, noting whether B0042 is current or historical and whether other airbag codes are present.
Check the vehicle history for collision repair, seat removal, trim work or water leaks near the third row.
Follow the manufacturer's procedure to make the system safe first (battery disconnection and wait time) before touching any airbag connector or wiring.
Visually inspect the third-row left harness, connectors and locking clips for chafing, pinching, corrosion, bent pins or unlatched plugs.
Check that the connectors are fully seated and that any shorting clips are intact, handling them as the manufacturer instructs.
Check circuit resistance and continuity only with the manufacturer's approved method. Never apply a test meter or power directly to a restraint device.
Compare the fault with the model-specific wiring diagram and restraint layout to confirm what this code covers on that vehicle.
After repair, clear the code and confirm it does not return and the warning light stays off.

How to fix

Repair or replace the damaged harness section, using the correct connectors and routing it clear of moving seat parts.
Clean, re-seat or replace corroded or damaged connectors.
Replace the faulty third-row restraint component if testing confirms it is at fault, following the manufacturer's procedure.
Repair the source of water ingress, then dry and renew any affected connectors.
Replace or reprogram the airbag control unit only after the wiring and restraint device have been ruled out and as the manufacturer specifies.

Can I keep driving?

High severity

The car may still drive normally, but the third-row left restraint may not work in a crash, so limit use, avoid carrying passengers in that seat and have the system inspected promptly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.