B0042 code meaning
Third Row Left Frontal Stage 2 Deployment Control
What B0042 means
B0042 stands for the second stage of a frontal airbag aimed at the left third-row passenger. A second stage only makes sense with an inflator that has two independently fired charges, as in Breed's multi-chamber design where the controller picks which chamber fires first and the gap between them. No carmaker documents B0042 for the third row, and no series car with such a bag is known. The older GM meaning is clear-cut: Saab's 9-5 (2006) and 9-3 manuals define B0042 as driver frontal stage 2 loop resistance below 1.5 ohms lasting 2 seconds, and the GM CPA retainer bulletin 08-09-41-002H covers it too. Airbag lamp on.
B0042 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 B0042
- Airbag warning lamp on
- Adaptive two-stage inflation for this seat is unavailable
- 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 B0042
- PossibleOpen or short only in the stage 2 wiring
- PossibleConnector lock not engaged at the airbag plug
- 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
Third row left frontal airbagSquib circuitSRS seat wiringSRS control module
What each part of B0042 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). |
| 42 | The exact fault in that area. |
What to do next
- Note B0042 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 B0042
What does B0042 mean?
B0042 means "Third Row Left Frontal Stage 2 Deployment Control". B0042 stands for the second stage of a frontal airbag aimed at the left third-row passenger. It is a generic code, so it means the same on every make.
Is it safe to drive with B0042?
B0042 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0042 fail an emissions test?
B0042 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 B0042 to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will B0042 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.