The Accessory Power Module (APM) controls the energy flowing between the high voltage, 300-volt, direct current (DC) and low voltage, 14-volt, DC to support the vehicles accessories and charge the 12-volt battery. The APM receives a 14-volt enable command from the Hybrid Powertrain Control Module (HPCM) over the high speed hybrid GMLAN communication circuit. APM functions will run only when the APM Enable is active on the high speed hybrid GMLAN communication circuit.

Heat is generated in the 14 volt APM circuit based on the current demand for the 14 volt systems. The engine control module (ECM) measures the temperature of the power electronics cooling loop and commands the flow of 2 electrical coolant pumps. The APM transfers heat in the 12 volt circuit to the APM heat plate which is then dissipated at the power electronics front end heat exchanger.

Ignition/Accessory On.

APM heat plate temperature rises above 105°C (221°F).

This DTC could be caused by a possible power electronics cooling system failure due to the following:

Schematic Reference

Hybrid Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Drive Motor Generator Control Module Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Review the Failure Records when the DTC set.

⇒	If the engine coolant temperature (ECT) was above 125°C (257°F) when the DTC set, go to Symptoms - Engine Cooling and correct that concern first.

2. Operate the vehicle while monitoring the APM heat plate temperature with the scan tool.
3. If the APM heat plate temperature is more than 100°C (212°F) proceed with Circuit/System Testing.

1. Inspect for proper coolant level in the hybrid cooling system reservoir.

⇒	If coolant level is low refer to Generator Control Module Cooling System Draining and Filling.

2. Inspect the hybrid cooling system radiator for debris or obstruction.

⇒	If a concern is found, repair or replace the restricted or damaged components as necessary.

3. Inspect for proper operation of all hybrid system coolant pumps.

⇒	If a concern is found, repair or replace the coolant pumps as necessary.

4. Command the cooling fans through all operating speeds.

⇒	If the cooling fans do not operate in all speeds, refer to Cooling Fan Inoperative.

5. If the above inspections do not identify a concern, disassemble the drive motor generator control module assembly and inspect the APM and PIM cooling surfaces for excessive corrosion or contamination restriction. Refer to Drive Motor Generator Power Inverter Module Removal and Installation.

⇒	If a concern is found, clean the APM and/or PIM cooling surfaces or replace the APM as necessary.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for APM replacement, setup, and programming