What P0A78 means
P0A78 means the inverter stage feeding drive motor A has reported a power-switch fault.
How the engine computer detects it
GM explains the check in its hybrid OBD tables: the IGBT module watches each phase for desaturation, a sign of a short between the upper and lower switch; if that status persists for about 2 ms the code sets as Type A, MIL on the first trip. Stellantis replaced the power inverter module on 2021 Jeep Wrangler 4xe with P0A78 and P0A79, which ran on engine power only, and refreshed hybrid control software on the 2017 Pacifica Hybrid. Land Rover logs P0A78 in the inverter converter of 2024-25 Range Rover models and asks not to clear it before diagnosis. P0A79 is motor B, P0A7A the generator inverter, P0A3C overheating of inverter A. Expect a warning and loss of electric drive.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- MIL and hybrid or high-voltage warning
- No electric drive, engine-only operation
- Stop safely warning on some models
Common causes
- IGBT desaturation or short in the inverter power stage Most likely
- Power inverter module defective (replaced on Jeep Wrangler 4xe) Most likely
- Hybrid control software requiring update Possible
- Shorted winding or phase cable of drive motor A Less likely
How to diagnose P0A78
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: inverter, drive motor a.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0A78 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Chrysler Pacifica Plug-In Hybrid | 2024 | 3 | — | |
| Chrysler Pacifica | 2021–2023 | 3 | — |
Counts of owner complaints to the NHTSA that mention P0A78 (14 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- A
- Hybrid and electric propulsion
- 78
- Specific fault
Questions drivers ask
Can I drive with code P0A78?
If the car drives normally, drive gently to a shop that services hybrids. If it shows a hybrid system warning, loses power or won't go into Ready, pull over and have it towed. Never touch orange high-voltage cables.
Will my car pass an emissions inspection with P0A78?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.