B0031 code meaning
Second Row Left Frontal Stage 1 Deployment Control
What B0031 means
B0031 points to the first firing stage of a frontal airbag that protects the left rear passenger, so it can only be stored where such a bag exists. The known production case is Mercedes-Benz's S-Class of 2020: an optional rear airbag (standard on the Maybach) unfolds from the back of the front seat for the two outer rear seats, built as a gas-filled tube frame that draws ambient air into its cushion. No carmaker publishes B0031 with this meaning. GM used the number differently: the Saab 9-4X 2011 manual groups B0031 with its front seat side airbag codes. Stage 2 and 3 of the same bag follow as B0032 and B0033. The airbag lamp lights and the rear bag may not fire in a frontal crash.
B0031 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0031
- Airbag warning lamp on
- Left rear passenger may lose frontal airbag protection in a crash
- 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 B0031
- Most likelyLoose or corroded connector of the airbag lead routed through the front seat backrest
- PossibleInternal fault in the rear-seat airbag module in the front seatback
- PossibleLead stretched or pinched by the seat track or folding mechanism
- Less likelyRestraint module configured for equipment the vehicle does not have (wrong part or coding)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Second row left frontal airbagSquib circuitSRS seat wiringSRS control module
What each part of B0031 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). |
| 31 | The exact fault in that area. |
What to do next
- Note B0031 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 B0031
What does B0031 mean?
B0031 means "Second Row Left Frontal Stage 1 Deployment Control". B0031 points to the first firing stage of a frontal airbag that protects the left rear passenger, so it can only be stored where such a bag exists. It is a generic code, so it means the same on every make.
Is it safe to drive with B0031?
B0031 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0031 fail an emissions test?
B0031 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 B0031 to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will B0031 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.