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B0040 — Third Row Left Side Airbag Deployment Control

Generic OBD-II · all makesBody

OBD-II code B0040 indicates a fault in the deployment control circuit for the third row left side airbag. This code is set when the airbag control module detects an open circuit, short circuit, or resistance out of range in the squib loop for that specific airbag. The airbag system will be disabled for that location until the fault is corrected.

Symptoms

What causes it — most likely first

1. Faulty third row left side airbag (squib)

The airbag inflator or its internal squib circuit is open, shorted, or has incorrect resistance, often due to age, manufacturing defect, or physical damage.

2. Damaged wiring or connectors in the airbag circuit

Wiring between the airbag control module and the third row left side airbag may be chafed, pinched, broken, or have corroded terminals, causing high resistance or open circuit.

3. Loose or corroded connector at the airbag or control module

Poor contact at the airbag connector or the module connector can cause intermittent or permanent circuit faults.

4. Short to ground or power in the deployment loop

Wiring insulation damage can cause the airbag circuit to short to vehicle ground or a power source, triggering the code.

5. Faulty airbag control module (SDM)

Internal failure of the sensing and diagnostic module (SDM) is possible but less common; it should be considered only after ruling out all other causes.

How it's diagnosed

  1. Retrieve all stored diagnostic trouble codes and freeze frame data using a scan tool.
  2. Disconnect the battery and wait at least 10 minutes for the airbag system capacitors to discharge before performing any circuit tests.
  3. Inspect the wiring harness and connectors between the airbag control module and the third row left side airbag for damage, corrosion, or loose connections.
  4. Measure the resistance of the airbag squib circuit at the module connector; compare to manufacturer specifications.
  5. Check for shorts to ground or power in the deployment loop wiring.
  6. If wiring and airbag test within specification, replace the airbag control module and verify the repair.

Code facts & related codes

SystemBody
StandardizationSAE generic — identical on every make
Related codesB0038 — Second Row Right Side Airbag DeploymenB0039 — Second Row Right Frontal Stage 1 DeploB0041 — Third Row Left Frontal Stage 1 DeploymB0042 — Third Row Left Frontal Stage 2 DeploymB0043 — Third Row Left Frontal Stage 3 DeploymB0048 — Third Row Right Side Airbag Deployment

Vehicles this code applies to

The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:

2005 Land Rover Freelander2005 Land Rover Range Rover

Frequently asked

Can I drive my vehicle with a B0040 code?

The vehicle will likely drive normally, but the third row left side airbag will not deploy in a crash, increasing the risk of injury to occupants in that seating position. It is recommended to repair the fault promptly.

Is it safe to diagnose this code myself?

Airbag systems contain explosive devices and stored energy. Improper handling can cause accidental deployment and serious injury. Diagnosis should be performed by a qualified technician with appropriate training and tools.

Will replacing the airbag control module fix B0040?

Not necessarily. The code is often caused by a faulty airbag, wiring, or connector. Replacing the module without proper diagnosis may not resolve the issue and is an expensive guess. The module should only be replaced after all other causes have been ruled out.

Can a weak battery cause this code?

While a weak battery is not a direct cause, low system voltage can cause erratic module behavior and may contribute to false codes. Ensure the battery and charging system are in good condition before extensive diagnosis.