Chassis, generic

C0901 TPMS Sensor 1 Position Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Learning drive too short or too slow after wheel change or sensor replacement
Wheel speed data from the ABS module missing or implausible, so phase comparison fails
Transmitters of a spare wheel or a nearby vehicle disturbing the assignment

Symptoms

  • TPMS warning lamp lit or flashing although tire pressures are correct
  • Pressures shown at the wrong wheel position or no position display at all

Repair estimate

DifficultyEasyDIY possible
Parts and labour€0–80
Time0.2–1 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

tpms sensortpms receiver

Related codes

C0903C0900C0912

References: saabwisonline.com, static.nhtsa.gov, patents.google.com.