P0A79: Drive Motor B Inverter Performance

P0A79 is the drive motor B counterpart of P0A78: the inverter stage for motor B has detected a power-switch fault. 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.

Symptoms

• MIL and hybrid system warning
• No electric drive, engine-only operation
• Loss of propulsion in severe cases

Most likely causes

• IGBT desaturation or short in the motor B power stage
• Power inverter module defective
• Loose high-voltage cable at the inverter terminal (Pacifica Hybrid)
• Hybrid control software requiring update

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. Compare the reading with other engine data while varying the engine speed.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0A79 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• A: Hybrid or air and fuel
• 79: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0A79?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0A79?

The most common causes are: iGBT desaturation or short in the motor B power stage; power inverter module defective; loose high-voltage cable at the inverter terminal (Pacifica Hybrid).

Related codes

• P0A78Drive Motor A Inverter Performance
• P0A7AGenerator Inverter Performance
• P0A3DDrive Motor B Inverter Over Temperature
• P0A1CDrive Motor B Control Module Performance
• P0A91Drive Motor B Performance

Sources

• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• gsi.ext.gm.com: 11OBDG01 HYBRID Diagnostics
• static.nhtsa.gov: MC 10242816 9999
• static.nhtsa.gov: MC 10224727 9999

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.