Powertrain, generic (extended)

P28C9 Clutch A Motor Overspeed

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P28C9 is stored when the clutch A motor turns faster than the controller considers plausible for the pressure it is asked to hold. Because the pump in such actuators delivers oil straight into the closed clutch circuit, the motor should slow down once pressure is reached; if it keeps racing, the oil is escaping or the pump is not loaded. Likely reasons are a leaking clutch piston seal, air drawn in at low fluid level, or a broken coupling between motor shaft and gerotor so that the motor spins free. A faulty rotor position signal can also fake a high speed, which is why P28CB/P28CC deserve a look first. P28CA is the opposite case. No carmaker publishes limits for P28C9.

Likely causes

Oil escaping from the clutch A pressure circuit, e.g. worn piston seal
Pump drawing air because of low fluid level or clogged suction filter
Broken drive between motor shaft and gerotor rotor
Faulty motor position signal reporting too high a speed

Symptoms

  • Clutch A slips or fails to transmit full torque
  • Transmission warning and restricted gear choice

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,800
Time0.5–5 h

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

Parts involved

clutch motor aclutch actuator a

Related codes

P28CAP28C8P28CBP28CCP28D8

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