Body, generic
B004A Third Row Right Frontal Stage 2 Deployment Control
Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo
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.
Likely causes
Open or short only in the stage 2 wiring
Loose connector in the second-row seatback
Restraint module configured for equipment the vehicle does not have (wrong part or coding)
Symptoms
- 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
Repair estimate
DifficultyShop_onlyWorkshop job
Parts and labour€100–1,200
Time1–4 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
third row right frontal airbagsquib circuitsrs seat wiringsrs control module
Related codes
References: patents.google.com, patents.google.com, patents.google.com.