Body, generic

B0042 Third Row Left Frontal Stage 2 Deployment Control

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Open or short only in the stage 2 wiring
Connector lock not engaged at the airbag plug
Restraint module configured for equipment the vehicle does not have (wrong part or coding)

Symptoms

  • 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

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 left frontal airbagsquib circuitsrs seat wiringsrs control module

Related codes

B0041B0043B004A

References: patents.google.com, saabwisonline.com, static.nhtsa.gov.