Cause
Faulty seat belt pretensioner
A seat belt pretensioner, or its circuit, is out of specification.
A pretensioner is a pyrotechnic device, and this is the part of the restraint system people are most surprised to find contains an explosive charge. In a crash it pulls several centimetres of slack out of the belt within a few milliseconds, so the occupant begins decelerating with the car rather than a moment after it. Without it the belt does not begin working until the body has already started moving.
Its circuit is monitored exactly like an airbag's — by measuring the initiator's resistance continuously — so the same rules apply: an open loop disables it, and often disables the whole restraint system with it, and an ordinary multimeter must never be put across the circuit because the measuring current can fire the device.
The commonest cause is the wiring rather than the pretensioner, because the harness runs under a seat that moves. Objects pushed beneath the seat, and seats removed for trimming or cleaning and refitted carelessly, account for a large share of these faults.
Two things worth checking before a part is ordered. A pretensioner that has already fired reads as an open loop and is not visible from outside — belts fire in impacts too mild to deploy an airbag. And on belts with more than one pretensioner, the letter in the code identifies which one: a retractor pretensioner winds slack onto the reel, a buckle pretensioner pulls the stalk down, an anchor pretensioner tightens the lap section at the floor.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (34)
Codes where this is a likely explanation first, rather than merely a possible one.
- B0070 Driver Seat Belt Pretensioner A Deployment Control Likely for this code High
- B0071 First Row Centre Seat Belt Pretensioner Deployment Control Likely for this code High
- B0072 Passenger Seat Belt Pretensioner A Deployment Control Likely for this code High
- B0073 Second Row Left Seat Belt Pretensioner Deployment Control Likely for this code High
- B0074 Second Row Centre Seat Belt Pretensioner Deployment Control Likely for this code High
- B0075 Second Row Right Seat Belt Pretensioner Deployment Control Likely for this code High
- B0076 Third Row Left Seat Belt Pretensioner Deployment Control Likely for this code High
- B0077 Third Row Centre Seat Belt Pretensioner Deployment Control Likely for this code High
- B0078 Third Row Right Seat Belt Pretensioner Deployment Control Likely for this code High
- B0079 Driver Seat Belt Pretensioner B Deployment Control Likely for this code High
- B007A Passenger Seat Belt Pretensioner B Deployment Control Likely for this code High
- B007B Second Row Left Seat Belt Pretensioner B Deployment Control Likely for this code High
- B007C Second Row Right Seat Belt Pretensioner B Deployment Control Likely for this code High
- B007D Second Row Centre Seat Belt Pretensioner B Deployment Control Likely for this code High
- B007E Driver Seat Belt Pretensioner C Deployment Control Likely for this code High
- B007F Passenger Seat Belt Pretensioner C Deployment Control Likely for this code High
- B0080 Driver Seat Belt Load Limiter Deployment Control Likely for this code High
- B0081 First Row Centre Seat Belt Load Limiter Deployment Control Likely for this code High
- B0082 Passenger Seat Belt Load Limiter Deployment Control Likely for this code High
- B0083 Second Row Left Seat Belt Load Limiter Deployment Control Likely for this code High
- B0084 Second Row Centre Seat Belt Load Limiter Deployment Control Likely for this code High
- B0085 Second Row Right Seat Belt Load Limiter Deployment Control Likely for this code High
- B0086 Third Row Left Seat Belt Load Limiter Deployment Control Likely for this code High
- B0087 Third Row Centre Seat Belt Load Limiter Deployment Control Likely for this code High
- B0088 Third Row Right Seat Belt Load Limiter Deployment Control Likely for this code High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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