What Does B0040 Mean?
This code indicates the airbag control module has detected a malfunction in the third row left side airbag deployment circuit or its associated components. The subfault designation suggests an internal circuit issue, wiring problem, or component resistance outside expected parameters in the deployment system. The airbag control module has logged this fault and typically disables the affected airbag to prevent inadvertent deployment or failure to deploy during a collision.
Safety Warning
This is a critical safety system fault that disables the third row left side airbag protection, leaving occupants in that seating position unprotected in a side impact collision. The vehicle should not be driven with passengers in the third row until repaired, and repair should be completed immediately by a qualified technician.
Common Causes
40%
Damaged or corroded wiring harness and connectors in third row seat area, often from cargo wear, moisture intrusion, or seat movement
30%
Faulty third row left side airbag module with internal circuit failure or out-of-range resistance
20%
Defective side impact sensor or pressure sensor on left side of third row
10%
Airbag control module internal fault or software issue affecting third row circuit monitoring
Diagnostic Steps
1
Step 1: Perform visual inspection of third row left side airbag wiring harness, connectors, and mounting points for signs of damage, corrosion, chafing, or moisture intrusion. Check connector terminals for bent pins or corrosion.
2
Step 2: Using a digital multimeter, measure resistance across the third row left side airbag deployment circuit at the airbag module connector (disconnected). Compare readings to manufacturer specifications, typically 2-3 ohms for side airbags.
3
Step 3: Check continuity and resistance of wiring harness between airbag control module and third row left side airbag connector. Verify no shorts to ground or open circuits exist in the deployment circuit.
4
Step 4: Test side impact sensor (if equipped) on left side third row by measuring sensor resistance and checking for proper voltage supply from airbag control module, typically 5V reference.
5
Step 5: If all wiring and sensors test within specifications, substitute known-good third row left side airbag module to isolate defective component. If fault persists, suspect airbag control module.
6
Step 6: Clear codes and perform airbag system self-test. Monitor live data for deployment circuit resistance values and verify fault does not return. Confirm airbag warning light extinguishes after successful repair.
Estimated Repair Cost
$300 - $1,800
Parts + labor, varies by vehicle and location
This code indicates the airbag control module has detected a malfunction in the third row left side airbag deployment circuit or its associated components. The subfault designation suggests an internal circuit issue, wiring problem, or component resistance outside expected parameters in the deployme...
The most common cause of B0040 (Third Row Left Side Airbag Deployment Control (Subfault)) is: Damaged or corroded wiring harness and connectors in third row seat area, often from cargo wear, moisture intrusion, or seat movement
Typical repair costs for B0040 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 disables the third row left side airbag protection, leaving occupants in that seating position unprotected in a side impact collision. The vehicle should not be driven with passengers in the third row until repaired, and repair should be completed immediately by a qualified technician.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B0040 to identify the root cause.
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Quick Info
Category
Body
System
Supplemental Restraint System (SRS)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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