Body, generic

B0039 Second Row Right Frontal Stage 1 Deployment Control

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Loose or corroded connector of the airbag lead routed through the front seat backrest
Internal fault in the right rear-seat airbag module
Lead stretched or pinched by the seat track or folding mechanism
Restraint module configured for equipment the vehicle does not have (wrong part or coding)

Symptoms

  • 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

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

second row right frontal airbagsquib circuitsrs seat wiringsrs control module

Related codes

B003AB003BB0031B0038

References: media.mbusa.com, patents.google.com, saabwisonline.com.