P28C4 code meaning
Clutch A Motor Phase U-V-W Circuit Low
Powertrain system Generic code P28xx codes Check engine light
What P28C4 means
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.
P28C4 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P28C4
- 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
Common causes of P28C4
- Most likelyPhase wire to the clutch A motor chafed through and touching ground
- PossibleWinding inside the clutch A motor shorted to the housing
- Less likelyDefective output transistor for the motor phases in the transmission controller
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Clutch motor aWiring harnessTCM
What each part of P28C4 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 8 | Area: transmission. |
| C4 | The exact fault in that area. |
What to do next
- Note P28C4 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P28C4
What does P28C4 mean?
P28C4 means "Clutch A Motor Phase U-V-W Circuit Low". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P28C4?
Drive gently and only to a workshop. With P28C4 the car can go into limp mode (reduced power) to protect itself.
Will P28C4 fail an emissions test?
Yes, it can. P28C4 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P28C4 to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P28C4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.