What does it mean?
B1391 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Passenger Seat Track Position Sensor Open or Short to Power .
Symptoms
- SRS lamp on with a passenger seat position circuit code
- Scan tool value pegged high or shown as invalid
- Passenger airbag deployment force uses its default setting rather than adapting to seat position
- The fault typically appears when the seat is moved or right after work under the seat
- No effect on engine or transmission operation
Likely causes
- Sensor connector under the passenger seat unplugged or only half-latched after seat or occupant sensor work
- Broken conductor in the section of under-seat loom that flexes as the seat is slid
- Signal wire chafed onto a powered seat circuit such as the passenger seat heater feed
- Sensor element internally open after damage or age
- Corroded terminal at the sensor or a bent pin at the module plug
- Sensor ground lost, which the module also treats as an out of range high reading
- Airbag control module input fault
How to fix it
- Check the live value and note whether it sits high, which is consistent with an open circuit or a short to power
- Power the restraint system down safely and wait the reserve power discharge time
- Verify that the under-seat connector is fully latched with no backed-out terminals
- Test the signal wire for continuity between the sensor and the module, and confirm a good sensor ground
- With the sensor unplugged and the ignition on, check the signal wire for battery voltage to identify a short to power
- Slide the seat through its whole travel while monitoring, to expose a wire that only breaks at one extreme
- Replace the sensor once the wiring and connector are proven good, then confirm the reading tracks the seat smoothly