Powertrain, generic (extended)

P28CA Clutch A Motor Underspeed

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P28CA means the clutch A motor stays below the speed the controller commands, so the pump cannot deliver oil fast enough to build or modulate clutch pressure. Mechanical drag is the usual culprit: particles wedged in the gerotor, a seized bearing, or very thick oil in deep cold. Stellantis reports debris blocking an actuator pump on the 7HDT300 (bulletin 21-040-26), though it lists P28C7 rather than this code. Electrical limits can play a part as well, for instance low supply voltage or the controller derating its output stage because of heat, which would appear as P28D1. Overspeed of the same motor is P28C9. No manufacturer documents P28CA with a threshold; engagement of clutch A becomes slow or fails.

Likely causes

Particles jamming the gerotor pump of clutch A
Stiff or seized motor/pump bearing
Low supply voltage to the actuator or poor ground

Symptoms

  • Clutch A engages late or with a jolt
  • Transmission warning, especially after cold start
  • Affected gears may be withheld

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time0.5–3 h

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

Parts involved

clutch motor aclutch actuator a

Related codes

P28C9P28C8P28D1P28CCP28D9

References: law.cornell.edu, cti-symposium.world, static.nhtsa.gov.