P28C4Clutch A Motor Phase U-V-W Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P28C4 means the transmission controller finds the voltage too low on a phase lead (U, V or W) of the electric motor that operates clutch A. This layout belongs to wet dual-clutch gearboxes without a valve block, such as the Getrag/Magna 7DCT300 and its hybrid derivative 7HDT300: a brushless motor per clutch spins a gerotor pump that feeds oil directly to the clutch piston. A phase pulled towards ground, for example by chafed insulation or a shorted driver transistor, is the typical trigger. P28C5 covers the opposite direction, P28C6 an interrupted phase. No manufacturer publishes a code-specific threshold; the driver loses the gears carried by clutch A and gets a transmission warning.
- What you may notice
- Transmission warning lamp, often together with the MIL
- Odd or even gears locked out, depending on which shaft clutch A serves
- Jerky or delayed pull-away
- Likely causes
- LikelyPhase wire to the clutch A motor chafed through and touching ground
- PossibleWinding inside the clutch A motor shorted to the housing
- RareDefective output transistor for the motor phases in the transmission controller
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.