Body, generic

B0056 Third Row Left Seat Belt Sensor

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

B0056 belongs to the left third-row seat's buckle sensor, found in larger SUVs, minivans and seven-seat estates. Third-row seats usually fold flat into the floor, so the buckle lead has to pass through the folding mechanism and is flexed every time the cargo area is extended. In Ford's patent for rear belt monitoring the third-row bench is the hard-wired part of the system, while only the removable second row needs a wireless link. FMVSS 208 S7.5(c) extends the rear belt warning to all rear rows for vehicles built from September 2028. A Hall switch that senses the latched tongue is the usual hardware. No carmaker documents B0056 with this wording publicly, nor does any service bulletin mention it; Mitsubishi's B0052 is the documented model for this fault type.

Likely causes

Buckle lead broken or chafed in the fold-flat mechanism of the third row
Loose or corroded connector at the third-row seat
Faulty sensor in the left third-row buckle

Symptoms

  • Airbag or rear belt warning lamp on
  • Fault may appear only with the third-row seat folded or raised
  • Safety note: third-row buckle plugs can sit near pretensioner wiring; only unplug them with the battery disconnected and the wait time observed

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€60–500
Time0.5–2.5 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

B0057B0058B0076

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