P0A78
DTC P0A78
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P0A78
-
Drive Motor Inverter Performance
Circuit/System Description
The generator control module also called the starter generator control module is comprised of the following three control modules; the hybrid powertrain control module, 14 volt power module and the drive motor control module. These three control modules are non serviceable and are part of the generator control module.
The drive motor control module operates the starter generator, also referred to as the drive motor, based upon hybrid powertrain control module commands. The drive motor control module controls the speed and output torque of the starter generator through the sequencing actuation of high current switching transistors called insulated gate bipolar transistors. Each insulated gate bipolar transistor assembly is monitored for fault conditions. The motor control module is part of the generator control module and is not serviced separately.
Conditions for Running the DTC
The high voltage contactor relay is closed.
Conditions for Setting the DTC
The drive motor control module detects excessive current flow through the switched portion of the insulated gate bipolar transistor.
Action Taken When the DTC Sets
* DTC P0A78 is a Type B DTC.
* The hybrid powertrain control module opens the high voltage contactor relay.
Conditions for Clearing the DTC
DTC P0A78 is a Type B DTC.
Reference Information
Schematic Reference
* Hybrid Controls Schematics Hybrid Controls Schematics
* Hybrid Energy Storage Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
* Starter Generator Description and Operation Starter Generator Description and Operation
* Generator Control Module Description and Operation Generator Control Module Description and Operation
* Hybrid Modes of Operation Description Hybrid Modes of Operation Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Circuit/System Verification
If the DTC is set, clear DTC; Turn the ignition OFF for 2 minutes. Turn the ignition ON, Operate vehicle within conditions for running and setting DTC. If the DTC resets, go to Circuit/System Testing.
Circuit/System Testing
Danger:
Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
The High Voltage Disabling procedure will perform the following tasks:
* Identify how to disable high voltage.
* Identify how to test for the presence of high voltage.
* Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
Failure to follow the procedures exactly as written may result in serious injury or death.
1. Perform the High Voltage Disabling High Voltage Disabling procedure.
2. Remove the 3-phase cables from the K59 starter generator control module.
3. Test for infinite resistance between the 3-Phase cable terminals listed below and ground for each phase of the drive motor generator battery cable:
* X8 phase U terminal
* X7 phase V terminal
* X6 phase W terminal
• If less than infinite resistance, test each phase of the drive motor generator battery cable for a short to ground. If the cables test normal, replace the A15 starter generator.
4. Disconnect the 3-phase cables from the A15 starter generator.
5. Test for infinite resistance between the 3-Phase circuits listed below for each phase of the Drive Motor Generator Battery Cable:
* Phase U and phase V
* Phase V and phase W
* Phase W and phase U
• If less than infinite resistance, replace the Drive Motor Generator Battery Cable.
6. Replace the A15 starter generator and retest for the DTC. If the DTC resets, replace the K59 starter generator control module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Starter Generator Replacement Starter Generator Replacement for starter generator replacement.
* Drive Motor Generator Battery Cable Replacement Drive Motor Generator Battery Cable Replacement for 3-Phase Cable Assembly replacement.
* Control Module References Programming and Relearning for Generator Control Module, also called the Starter Generator Control Module, replacement, programming and setup.