B003B code meaning
Second Row Right Frontal Stage 3 Deployment Control
What B003B means
B003B is the third firing element of the right rear-seat frontal airbag. In front airbags Mercedes-Benz uses this third position for the squib that opens a vent valve and lets gas escape (B000313 driver, B001213 passenger); a patent from Breed shows the other option, a third gas chamber with its own igniter that the controller can fire later, for example in a second impact. Which of these a rear bag would use is not published, and no carmaker documents B003B. If it is stored, the module has found the third element out of range in resistance or voltage. Stage 1 and 2 of the same bag report as B0039 and B003A. The airbag lamp stays on.
B003B 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 B003B
- Airbag warning lamp on
- Right rear airbag may deploy without its adaptive third stage
- 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 B003B
- Most likelyLoose or corroded connector of the airbag lead routed through the front seat backrest
- PossibleDamaged stage 3 lead or vent squib in the right rear airbag
- 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 B003B 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). |
| 3B | The exact fault in that area. |
What to do next
- Note B003B 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 B003B
What does B003B mean?
B003B means "Second Row Right Frontal Stage 3 Deployment Control". B003B is the third firing element of the right rear-seat frontal airbag. It is a generic code, so it means the same on every make.
Is it safe to drive with B003B?
B003B does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B003B fail an emissions test?
B003B 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 B003B to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will B003B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.