What does it mean?
B1339 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Front Impact Sensor Fault .
Symptoms
- Airbag warning lamp on and the restraint system will not arm
- Airbags and belt pretensioners may not fire in a collision
- The fault reappears on every ignition cycle
- The restraint system self-test never completes on a scan tool
- No change in engine or transmission behaviour
Likely causes
- Open circuit or high resistance in the front impact sensor circuit
- Corroded terminals at the sensor connector or at the restraint control module
- Loom damaged during a front-end repair or bumper removal
- Impact sensor internally faulty and sending data that does not agree with the other sensors
- Sensor mounting loose so its readings do not match vehicle motion
- Moisture inside the connector after driving through deep water
- Restraint control module input failure
How to fix it
- Disconnect the battery and observe the required waiting time before touching restraint wiring
- Inspect and reseat the sensor connector, checking for corrosion and spread terminals
- Measure the resistance of both sensor circuits from the restraint module connector
- Wiggle-test the front harness while watching for intermittent resistance changes
- Verify the sensor mounting bolts and bracket are correct, straight and tight
- Repair the harness using the approved restraint repair method rather than a temporary splice
- Replace the front impact sensor as the final step, then clear codes and verify the lamp self-test passes