Body, generic

B0053 Second Row Left Seat Belt Sensor

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

B0053 is the J2012 slot for the buckle sensor at the second row's left seat. Rear buckle sensors drive the rear belt reminder: for vehicles built from September 2028, FMVSS 208 S7.5(c) demands a start-up display of which rear belts are fastened or open and a warning when one is unlatched while driving. No carmaker documents B0053 with this meaning publicly; the closest documented case is Mitsubishi's passenger code B0052, set for an open, shorted or invalid buckle signal lasting 2 seconds. Older GM airbag modules give the number another meaning: the Saab 9-3 and the 2006 Saab 9-5 store B0053 when a deployment was commanded while a firing loop fault was present, a code that cannot be erased after a front airbag deployment.

Likely causes

Loose or corroded buckle connector under the left rear seat
Faulty switch or Hall sensor in the left rear buckle
Lead damaged by folding or sliding the second-row seat
Older GM/Saab module: deployment record with a loop fault, module replacement needed

Symptoms

  • Airbag or rear belt warning lamp on
  • Rear belt display shows the left seat wrongly as fastened or unfastened
  • Safety note: the buckle plug sits under the seat near pretensioner and side airbag plugs; only unplug it with the battery disconnected and the wait time observed

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€60–450
Time0.5–2 h

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

Parts involved

seat belt buckle switchsrs seat wiringsrs control module

Related codes

B0054B0055B0073B0052

References: law.cornell.edu, patents.google.com, mitsubishitechinfo.com, saabwisonline.com.