Body, generic

B0021 Left Curtain Deployment Control 1

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

In the J2012 order B0021 is the first firing loop of the left curtain airbag, the bag that drops from the roof rail over the side windows. Mitsubishi files it under the left curtain module and stores byte 11, 12, 13 or a short to another circuit once the condition has lasted 2 seconds. Mercedes-Benz reads B002113 as an open squib of the left window bag on the A-Class, CLA and GLB, where raised contact resistance at the restraint unit plug was the cause (LI54.21-P-070658). Curtain 1 is the only or front curtain inflator; B0022 is the second one. GM Global A modules use B0021 for the passenger seat side airbag instead, with bulletins on seat harness contact (PI1469, 23-NA-030). Airbag lamp on; the left curtain may not fire.

Likely causes

Raised contact resistance at the curtain airbag or restraint module connector
Damaged lead along the A-, B- or C-pillar or the roof rail
Internal fault in the left curtain airbag module
Fault or unsuitable software in the restraint control module

Symptoms

  • Airbag warning lamp on
  • Left curtain airbag may not deploy in a side impact or rollover
  • 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€100–1,000
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

left curtain airbagsrs roof wiringsrs control module

Related codes

B0022B0029B0020B0046

References: mitsubishitechinfo.com, mitsubishitechinfo.com, mitsubishitechinfo.com, static.nhtsa.gov.