What does it mean?
B1398 is a Body (airbags, seat belts, body electronics) fault code. It indicates: STPS (Seat Track Position Sensor) - Passenger Open or Short to Ground .
Symptoms
- SRS lamp on with a passenger seat position circuit code
- Scan tool value sits at the bottom of the range and ignores seat movement
- Passenger airbag deployment force uses its default setting
- Fault may come and go as the passenger seat is moved or as passengers shift their weight
- No effect on running or driveability
Likely causes
- Signal wire rubbed bare against the passenger seat frame, rail or a floor bracket
- Open circuit in the under-seat loom where it bends every time the seat is adjusted
- Water in the passenger footwell reaching the seat connector and giving a path to ground
- Loom pinched under the seat pan when the seat was bolted back into place
- Sensor failed with its output permanently low
- Corroded terminals at the sensor connector, which sits low and collects damp
- Airbag control module input stage fault
How to fix it
- Note the live value and slide the passenger seat to see whether the reading responds at all
- Power down the restraint system safely and observe the reserve power discharge time
- Unplug the sensor and check the signal wire to body ground; a low reading proves the harness is shorted
- If the wire is not shorted, check it end to end for continuity to locate an open
- Inspect the loom along the seat rail and floor brackets for bare copper and crush marks
- Dry the connector and trace the source of any footwell water before repairing
- Replace the sensor once the wiring and connector are proven good, then verify the value moves smoothly with the seat