Powertrain, generic (extended)

P28DB Clutch B Motor Position Sensor Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P28DB flags a rotor position signal for the clutch B motor that is electrically present but fails the plausibility tests: angle steps arrive in a wrong order, a transition is skipped, or the derived speed disagrees with the phase currents and the measured clutch pressure. CARB 13 CCR 1968.2 calls for such rationality monitoring of input signals where it is technically feasible, beyond pure circuit checks. Interference through a damaged screen, a wire strand partly broken, a sensor or target magnet that has shifted, or metallic debris on the target are typical findings. Because commutation then goes wrong, the motor may judder or stall and P28D8 or P28D9 can follow. P28DA is the hard circuit fault, P28CC the clutch A twin. No carmaker documents P28DB.

Likely causes

Electrical interference through a damaged screen on the sensor lead
Partly broken strand in the clutch B position sensor wiring
Sensor or target magnet shifted, or metallic debris on the target

Symptoms

  • Clutch B engages roughly or drops out intermittently
  • Transmission warning, sometimes only after several trips
  • Motor speed codes for clutch B stored alongside

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,300
Time0.5–3.5 h

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

Parts involved

clutch motor position sensor bwiring harnesstcm

Related codes

P28DAP28D8P28D9P28CC

References: law.cornell.edu, cti-symposium.world.