Airbags

B0057 — Third-Row Center Seat Belt Sensor Circuit Fault

Severity: medium Safe to drive

What B0057 means

The SRS control module constantly reads a sensor in the third-row center seat belt buckle to know whether that seat is occupied and buckled. B0057 sets when the signal from this circuit is missing, erratic or out of range. The cause can be the buckle sensor, its wiring or connector, or less often a control module.

Symptoms

  • Third-row center belt reminder light stays on
  • Belt chime keeps sounding even when buckled
  • SRS/airbag warning light may come on
  • Restraint features for that seat may be disabled or behave incorrectly

Possible causes

  1. Faulty buckle sensor in the third-row center seat belt
  2. Damaged or corroded wiring or connector in the sensor circuit
  3. Open circuit or short to ground or power in the harness under the seat
  4. Communication error between the SRS module and the body control module (BCM)
  5. Faulty SRS module or software mismatch after an update (uncommon)

How to diagnose

  1. Scan all modules, including SRS, and save the freeze-frame data
  2. Check for debris, spilled liquid or objects around the buckle and under the seat
  3. Inspect the buckle connector and harness for corrosion, chafing and a loose fit
  4. Watch live data to see whether the sensor state changes when the belt is buckled and unbuckled
  5. With the battery disconnected and SRS safety precautions followed, test circuit continuity and resistance per the factory wiring diagram
  6. Check for shorts to ground or voltage and verify supply and ground at the connector
  7. If wiring is good, replace the buckle assembly and see whether the fault clears
  8. Clear the code and confirm it does not return

Common fixes

  • Replace the seat belt buckle with its sensor
  • Repair the harness or replace a corroded connector
  • Clean the contacts and secure the wiring
  • Update software or replace the SRS/BCM module if confirmed faulty

Questions and answers

What does B0057 mean?

It indicates a fault in the third-row center seat belt sensor circuit. The SRS module is not getting a valid signal about whether the belt is buckled.

Can I drive with B0057?

Yes, it does not affect how the car runs. But protection for that seat may not work correctly, so get it checked soon.

Why does the belt chime never stop?

The module cannot read the buckle sensor and assumes the belt is unfastened. A bad buckle sensor or a corroded connector under the seat is the most common cause.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.