B0040 code meaning
Third Row Left Side Airbag Deployment Control
What B0040 means
B0040 is reserved for a side airbag at the left seat of a third row, as found in some seven-seat SUVs and vans; most of them protect that row only with an extended curtain. A Joyson (TK Holdings) patent states its seatback side module may serve any row, third included, and a GM application gives rear-row side bags their own gas generators and allows the rear row to be the third. No maker documents B0040 with this meaning. Earlier GM modules assign it elsewhere: Saab manuals for the 9-5 of 2006 and the 9-3 treat B0040 as low resistance in the driver side airbag loop, under 1.5 ohms with 0.2 tolerance for 2 seconds; bulletin 08-09-41-002H also names it for loose CPA retainers. Airbag lamp on.
B0040 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0040
- Airbag warning lamp on
- Left third-row occupant may lack side airbag protection
- Safety note: do not probe the airbag circuit yourself; unplug airbag connectors only with the battery disconnected and the stated wait time observed
Common causes of B0040
- Most likelyPoor contact at the side airbag connector of the third-row seat or rear quarter trim
- PossibleLead strained by folding or removing the third-row seat
- Less likelyInternal fault in the third-row side airbag
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Third row left side airbagSquib circuitSRS wiringSRS control module
What each part of B0040 means
| B | Body system: airbags, seat belts, power seats, lights and climate control. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 40 | The exact fault in that area. |
What to do next
- Note B0040 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about B0040
What does B0040 mean?
B0040 means "Third Row Left Side Airbag Deployment Control". B0040 is reserved for a side airbag at the left seat of a third row, as found in some seven-seat SUVs and vans; most of them protect that row only with an extended curtain. It is a generic code, so it means the same on every make.
Is it safe to drive with B0040?
B0040 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0040 fail an emissions test?
B0040 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is B0040 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will B0040 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.