P0C28Electric/Auxiliary Transmission Fluid Pump A Motor Current High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- MIL or service wrench lamp
- Auxiliary pump shuts down, no auto-stop or electric mode
- Likely causes
- 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
- RareCurrent sensing or power stage in the pump inverter faulty
- 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: €50 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.