B0039 code meaning
Second Row Right Frontal Stage 1 Deployment Control
What B0039 means
B0039 belongs to the right-hand rear-seat frontal airbag, stage 1, which is the primary charge that the module fires in any frontal crash severe enough to need the bag. The bag sits in the back of the passenger seat ahead; Mercedes-Benz offers this layout as an S-Class option and fits it as standard to the Maybach, where it is meant to ease head and neck loads on belted outer rear passengers. An older Daimler application already described a bag at the rear of a front seat that spreads a channel frame and fills with ambient air. No public DTC table pairs B0039 with this bag. GM Global A modules use B0039 for the right rear belt pretensioner instead (Saab 9-4X 2011). Airbag lamp on.
B0039 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 B0039
- Airbag warning lamp on
- Right rear passenger may lose frontal 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 B0039
- Most likelyLoose or corroded connector of the airbag lead routed through the front seat backrest
- PossibleInternal fault in the right rear-seat airbag module
- 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 right frontal airbagSquib circuitSRS seat wiringSRS control module
What each part of B0039 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). |
| 39 | The exact fault in that area. |
What to do next
- Note B0039 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 B0039
What does B0039 mean?
B0039 means "Second Row Right Frontal Stage 1 Deployment Control". B0039 belongs to the right-hand rear-seat frontal airbag, stage 1, which is the primary charge that the module fires in any frontal crash severe enough to need the bag. It is a generic code, so it means the same on every make.
Is it safe to drive with B0039?
B0039 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0039 fail an emissions test?
B0039 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 B0039 to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will B0039 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.