What P0A79 means
P0A79 is the drive motor B counterpart of P0A78: the inverter stage for motor B has detected a power-switch fault.
How the engine computer detects it
In GM hybrid OBD tables the IGBT module reports a desaturation status on a high or low side switch of any phase; persisting for about 2 ms it sets P0A79 as Type A with MIL on the first trip. Stellantis documents P0A79 several times: on the 2021 Jeep Wrangler 4xe together with P0A78 and an engine-only limp mode, fixed by a new power inverter module; on the 2017 Pacifica Hybrid with improved hybrid control software, and with a loose high-voltage cable at the inverter terminal that also caused loss of propulsion. P0A78 is motor A, P0A7A the generator inverter, P0A3D overheating of inverter B. The driver loses electric drive.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- MIL and hybrid system warning
- No electric drive, engine-only operation
- Loss of propulsion in severe cases
Common causes
- IGBT desaturation or short in the motor B power stage Most likely
- Power inverter module defective Most likely
- Loose high-voltage cable at the inverter terminal (Pacifica Hybrid) Possible
- Hybrid control software requiring update Possible
How to diagnose P0A79
- 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: drive motor b inverter, hybrid control module.
- 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.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- A
- Hybrid and electric propulsion
- 79
- Specific fault
Questions drivers ask
Can I drive with code P0A79?
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 P0A79?
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.