B004A code meaning
Third Row Right Frontal Stage 2 Deployment Control
What B004A means
B004A is the second-stage loop of the right third-row frontal airbag. Stage 2 is a separately ignited charge: Breed's patent shows an inflator whose chambers each carry their own igniter, fired alone, together or with a delay chosen by the controller, and Mercedes-Benz's rear airbag filing allows one deployment device per chamber for sequential filling. No published DTC table, vehicle maker or bulletin connects B004A to a real vehicle. If it appears, the stage 2 circuit of that bag is out of range while stage 1 (B0049) may still be fine; the left-hand equivalent is B0042. Airbag lamp on.
B004A 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 B004A
- Airbag warning lamp on
- Two-stage inflation for the right third-row seat is lost
- 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 B004A
- PossibleOpen or short only in the stage 2 wiring
- PossibleLoose connector in the second-row seatback
- 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 right frontal airbagSquib circuitSRS seat wiringSRS control module
What each part of B004A 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). |
| 4A | The exact fault in that area. |
What to do next
- Note B004A 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 B004A
What does B004A mean?
B004A means "Third Row Right Frontal Stage 2 Deployment Control". B004A is the second-stage loop of the right third-row frontal airbag. It is a generic code, so it means the same on every make.
Is it safe to drive with B004A?
B004A does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B004A fail an emissions test?
B004A 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 B004A to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will B004A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.