Powertrain, generic (extended)

P28EF Engine Disconnect Clutch Actuator Performance/Stuck Off

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

In a P2 hybrid a clutch placed between combustion engine and e-machine lets the car drive electrically with the engine at rest and couples the engine back in when it is needed. P28EF says the device that applies this clutch is not doing its job: it is commanded to act, but the expected pressure or clutch response stays absent, so the actuator behaves as if switched off. No manufacturer documents P28EF publicly. On Audi's A3 e-tron the clutch is applied through a pressure regulating valve in the mechatronic unit, and a mechanically faulty valve there produced the neighbouring code P2884 (clutch stuck open); a Ford patent feeds the clutch valves from hydraulic pumps. CARB counts such hybrid parts as monitored output components. The engine may then fail to join in or to start.

Likely causes

Pressure regulating valve of the disconnect clutch sticking or mechanically faulty
Contaminated or low transmission fluid, so the actuator cannot build pressure
Electric or mechanical oil pump delivers too little pressure to the clutch circuit
Control software or learned clutch values out of date

Symptoms

  • Engine does not start or does not engage while driving in hybrid mode
  • Gearbox or hybrid system warning in the cluster
  • Reduced power or electric-only limp mode

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–3,000
Time1–8 h

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

Parts involved

engine disconnect clutch actuatorhybrid control module

Related codes

P28F0P28F6P2884P2885P287EP2D8D

References: law.cornell.edu, static.nhtsa.gov, patents.google.com.