P28EF
Engine Disconnect Clutch Actuator Performance/Stuck Off
The engine disconnect clutch actuator is commanded to engage but does not produce the expected motion. Actuator stuck in disengaged position.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Actuator mechanically stuck offCommon
- Hydraulic engagement pressure lostPossible
- Carbon or debris buildup preventing free movementLess likely
Parts involved
- Engine Disconnect Clutch Actuator
- Hybrid Control Module
P28EF is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.