P0C28 code meaning
Electric/Auxiliary Transmission Fluid Pump A Motor Current High
Powertrain system Generic code P0Cxx codes Check engine light
What P0C28 means
P0C28 is the overcurrent protection of auxiliary pump motor A. GM uses it on Volt, ELR and later hybrids: the inverter trips when any of the U, V or W phases exceeds 35 A, in 2016 within about 4 ms of a 62 ms window, or when the d-axis current falls below a stator temperature limit, Type A, MIL on the first trip. GM service update 18199 for the 2018 Cadillac CT6 plug-in traces P0C28 to a faulty pump restart logic in the software. Ford's TSB 18-2282 lists P0C27 and/or P0C28 on the 2013-17 Fusion Energi and C-Max Energi, fixed by reprogramming the PCM and hybrid module; Ford also reports P0C28 in the SOBDMC of the 2024-25 Mustang Mach-E LFP, solved by software. P0C27 is the low side.
P0C28 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0C28
- MIL or service wrench lamp
- Auxiliary pump shuts down, no auto-stop or electric mode
Common causes of P0C28
- Most likelyPump control software faulty (Cadillac CT6 update 18199, Ford Energi TSB 18-2282)
- PossiblePump seized, contaminated or running against blocked flow
- PossibleShort between motor phases or to ground
- Less likelyCurrent sensing or power stage in the pump inverter faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aux trans pump a motor
What each part of P0C28 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| C | Area: hybrid propulsion. |
| 28 | The exact fault in that area. |
What to do next
- Note P0C28 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 P0C28
What does P0C28 mean?
P0C28 means "Electric/Auxiliary Transmission Fluid Pump A Motor Current High". P0C28 is the overcurrent protection of auxiliary pump motor A. It is a generic code, so it means the same on every make.
Is it safe to drive with P0C28?
Drive gently and only to a workshop. With P0C28 the car can go into limp mode (reduced power) to protect itself.
Will P0C28 fail an emissions test?
Yes, it can. P0C28 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 P0C28 to fix?
Difficulty: hard. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P0C28 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.