Powertrain, generic · Hybrid propulsion

P0A79 Drive Motor B Inverter Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

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

Symptoms

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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–6,000
Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

drive motor b inverterhybrid control module

Related codes

P0A78P0A7AP0A3DP0A1CP0A91

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.