Damaged, corroded or loose connector at the third row centre seat belt retractor or pretensioner; Wiring damage in the circuit, such as chafing, an open circuit, or a short to ground or voltage, often from seat movement, folding mechanisms or cargo; Faulty or previously deployed pretensioner or retractor assembly with out-of-range resistance; Poor connection at an in-line connector under the seat, in the load area trim or beneath the carpet, possibly from water ingress; Fault in the restraint control module, including internal driver failure; Damage from earlier crash repair or incorrect seat belt refitting, such as a pinched harness or a wrongly fitted part.

B0077

Third Row Center Seat Belt Pretensioner Deployment Control.

Generic
Body
Generic code
Medium severity

How this code is built

B: SystemBody
0: Defined bySAE, the same on every car
0: AreaBody area 0
77: FaultThe specific fault in that area

What it means

B0077 means the restraint control module has found a fault in the deployment control circuit for the third row centre seat belt pretensioner. The module checks the pretensioner's firing circuit (the squib) for correct resistance and voltage, and sets the code when the reading is out of range, open, shorted or otherwise implausible. The exact circuit layout and which seats have this fitting depend on the vehicle, so check the model's wiring information.

Symptoms

Airbag or SRS warning light on in the instrument cluster
Restraint system fault message on the display
Third row centre seat belt may not tighten in a collision, though this is not noticeable in normal driving
Other restraint faults stored alongside it, such as other seat belt or airbag circuit codes
Warning light stays on after the code is cleared

Possible causes

Damaged, corroded or loose connector at the third row centre seat belt retractor or pretensionerlikely
Wiring damage in the circuit, such as chafing, an open circuit, or a short to ground or voltage, often from seat movement, folding mechanisms or cargolikely
Faulty or previously deployed pretensioner or retractor assembly with out-of-range resistancepossible
Poor connection at an in-line connector under the seat, in the load area trim or beneath the carpet, possibly from water ingresspossible
Fault in the restraint control module, including internal driver failurerare
Damage from earlier crash repair or incorrect seat belt refitting, such as a pinched harness or a wrongly fitted partrare

How to diagnose

Read all stored codes and freeze frame data, noting whether B0077 is current or historic and whether other restraint codes are present
Check the vehicle history for crash damage, seat belt replacement or recent work on the rear seats or trim
Disconnect the battery and wait the time stated by the manufacturer before touching any restraint component, then visually inspect the third row centre belt, its connector and the nearby harness for damage, water or corrosion
Check the connector for bent, pushed-back or corroded terminals and for correct locking, including any shorting clip or locking device
Follow the manufacturer's procedure for circuit resistance checks. Never probe the pretensioner circuit with a test lamp or a meter that is not approved for restraint circuits
Inspect the harness route along the seat frame, floor and trim for chafing, pinching or previous repairs
Reconnect everything correctly, clear the code and recheck. If it returns immediately, the fault is likely in the pretensioner, the wiring or the control module
Check for software updates or technical bulletins for the specific model if no physical fault is found

How to fix

Clean or repair the connector, or replace it if the terminals are damaged or corroded
Repair or replace the damaged section of wiring using the manufacturer's approved repair method for restraint circuits
Replace the pretensioner or seat belt retractor assembly if it is faulty or has been deployed
Dry and treat any water ingress, then fix the leak that caused it
Replace or reprogramme the restraint control module only after wiring and components are proven good and the manufacturer's procedure calls for it
After repair, clear the codes and confirm the warning light stays off with no further restraint faults

Can I keep driving?

Medium severity

The car can usually be driven, but the restraint system may not protect the occupant of that seat properly in a collision, so avoid using the third row centre seat until it is repaired. Book it in soon, and have only a qualified technician work on restraint components.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.