Airbags

B0131 — Passenger Seat Belt Buckle Pretensioner Circuit Fault

Severity: medium Drive with care, to a shop

What B0131 means

The airbag (SRS) control module continuously tests the circuit of the pretensioner squib in the front passenger's belt buckle. B0131 is stored when the circuit resistance is out of range because of an open, short or poor connection. The system can't be sure the pretensioner will fire in a crash, so the SRS light comes on.

Symptoms

  • SRS/airbag warning light on or flashing
  • Passenger belt pretensioner may not fire in a crash
  • Light may go out and return when the seat is moved or bumped
  • Seat belt reminder behaving oddly for the passenger seat

Possible causes

  1. Faulty passenger belt buckle assembly with pretensioner
  2. Loose or corroded connector under the passenger seat
  3. Damaged or chafed wiring under the seat
  4. Occupancy sensor harness interfering with or damaging the pretensioner wiring
  5. Rarely, a failed SRS control module

How to diagnose

  1. Scan with a tool that reads SRS codes, note all stored codes, clear and see if B0131 returns
  2. Inspect the harness and connectors under the passenger seat for pinching, strain, water and corrosion
  3. Check that the occupancy sensor harness isn't pinching or rubbing the pretensioner wires
  4. Inspect the buckle connector pins and make sure it latches fully
  5. Measure circuit resistance only per the manufacturer's procedure with the battery disconnected, and never probe the squib with an ordinary multimeter
  6. Swap in a known-good buckle assembly to see if the code clears

Common fixes

  • Clean, secure or replace the connector under the seat
  • Repair or replace the damaged wiring section
  • Replace the passenger buckle and pretensioner assembly
  • Reroute the seat and occupancy sensor harnesses correctly
  • Replace the SRS module only if the fault is confirmed there

Questions and answers

Can I test the pretensioner circuit with a multimeter?

No, that's unsafe. Test current can fire the squib. Work on SRS circuits should be done with the battery disconnected and per factory procedure, ideally by a shop.

Why did B0131 appear after moving the seat or cleaning the interior?

Connectors and wiring under the seat are easy to bump or loosen. A poor connection causes a momentary open circuit and sets the code.

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.