Fault Family System: Powertrain (P-Codes) 6 SAE Codes

Motor Generator Inverter Performance

Diagnostic & Technical Explanation

Code P0A78 sets when the drive motor / generator inverter power stage cannot deliver the torque or bus voltage the control module commands, or an internal self-test detects a fault in the switching stage. The most common physical causes are insufficient inverter cooling, a degraded gate-driver or IGBT/MOSFET module inside the inverter, and a marginal HV bus connection that cannot supply the commanded current.

These 6 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 6 times.

Codes in this family (6)

Code	Definition	Repair coverage
P0A78	Drive Motor A Inverter Performance	3 ranked fixes
P0A79	Drive Motor B Inverter Performance	3 ranked fixes
P0A7A	Generator Inverter Performance	3 ranked fixes
P0C79	Drive Motor A Inverter Voltage Too High	3 ranked fixes
P0C7A	Drive Motor B Inverter Voltage Too High	3 ranked fixes
P0C7B	Generator Inverter Voltage Too High	3 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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