C0901TPMS Sensor 1 Position Performance
- Generic OBD-II code · Chassis
- Needs a drive cycle to confirm a fix
- How the car detects it
- Nothing public ties C0901 to a carmaker: no public code list, NHTSA bulletin or service index contains it. Its title concerns the automatic assignment of wheel transmitter 1 to a corner of the car. Without that link the system knows a pressure value but not which tire it belongs to. Saab's 9-5 of 2011 learns the side from the sensor's turning direction and the axle from signal strength, which takes 3 to 9 minutes of driving. A Schrader patent instead compares the phase angle each sensor reports with ABS tooth counts and picks the best matching wheel. Land Rover's TPM module sets C1D18-55 while locations are still unknown and clears it after 10 minutes above 20 km/h. A performance fault means the learning did not finish or gave a doubtful result.
- What you may notice
- TPMS warning lamp lit or flashing although tire pressures are correct
- Pressures shown at the wrong wheel position or no position display at all
- Likely causes
- LikelyLearning drive too short or too slow after wheel change or sensor replacement
- PossibleWheel speed data from the ABS module missing or implausible, so phase comparison fails
- RareTransmitters of a spare wheel or a nearby vehicle disturbing the assignment
- Repair
- Easy · Often possible to do yourself.Typical cost: €0 – €80
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.