Damaged or disconnected connector at the third row left side airbag or its wiring, often after seat or trim removal; Open or short circuit in the airbag squib wiring, for example chafed or pinched cable behind trim or under a seat; Poor terminal contact or corrosion in the airbag circuit connectors, including connectors under the seats or in the pillar; Faulty airbag module or igniter with out-of-range resistance; Clock spring or inline connector fault if the circuit routes through it (model dependent); Fault within the restraint control module.

B0040

Third Row Left Side Airbag 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
40: FaultThe specific fault in that area

What it means

B0040 is a generic body code relating to the third row left side airbag deployment control circuit. The restraint control module monitors the squib (igniter) circuit for this airbag and has detected a fault, such as an open circuit, short circuit or abnormal resistance. The exact airbag fitted in this position, and how the circuit is wired, depends on the vehicle, so check the manufacturer's data for the model.

Symptoms

Airbag or SRS warning light on the dashboard
Warning light stays on after ignition-on bulb check
Third row left side airbag may not deploy in a collision
Other airbag fault codes stored alongside it
Seat belt pretensioner or related SRS warning message on some models

Possible causes

Damaged or disconnected connector at the third row left side airbag or its wiring, often after seat or trim removallikely
Open or short circuit in the airbag squib wiring, for example chafed or pinched cable behind trim or under a seatlikely
Poor terminal contact or corrosion in the airbag circuit connectors, including connectors under the seats or in the pillarpossible
Faulty airbag module or igniter with out-of-range resistancepossible
Clock spring or inline connector fault if the circuit routes through it (model dependent)rare
Fault within the restraint control modulerare

How to diagnose

Read all stored codes and freeze frame data, noting whether the fault is current or history and whether other SRS codes are present
Ask about recent work such as seat removal, trim removal, upholstery repairs or collision damage, which often disturb airbag connectors
Visually inspect the third row left side airbag wiring and connectors for damage, pinching, corrosion or loose locking tabs
Check the manufacturer's procedure for safely isolating the SRS system before touching any airbag connector, then follow it exactly
Using the manufacturer's procedure, check circuit continuity and resistance between the restraint control module and the airbag, without applying test voltage to the squib
Check the reading against the manufacturer's specification to find whether the fault is in the wiring or the airbag module
Clear the code after repair, then recheck that the SRS light goes out and the code does not return

How to fix

Reseat or replace damaged connectors and repair any terminal contact problems
Repair or replace damaged airbag wiring, using the manufacturer's approved repair method
Replace the faulty third row left side airbag module or igniter if it is confirmed out of specification
Replace the clock spring or inline connector if the model routes the circuit through it and it is confirmed faulty
Replace or reprogram the restraint control module only if all wiring and components are proven good, following the manufacturer's procedure

Can I keep driving?

High severity

The airbag in this position may not deploy in a crash, so the SRS system is compromised. Limit driving and have it inspected promptly, especially if the third row is occupied.

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