P0AF7

DTC P0AF7

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptor
DTC P0AF7
- 14 Volt Power Module Overtemperature

Circuit/System Description

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 and the radiator fan. The APM transfers heat in the 12 volt circuit to the APM heat plate which is then dissipated at the generator control module coolant radiator.

Conditions for Running the DTC

Ignition/Accessory On.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

* DTC P0AF7 is a Type C DTC.
* The HPCM stores the DTC information in memory when the diagnostic runs and fails.
* The APM will disable 14 volt power conversion or Jump Assist.

Conditions for Clearing the DTC

* APM heat plate temperature falls below 95°C (203°F).
* DTC P0AF7 is a Type C DTC.

Diagnostic Aids

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

* Restricted radiator air flow or coolant fans inoperative.
* Restricted power electronics coolant flow or contaminated coolant.
* Inoperative power electronics cooling system pumps.

Reference Information
Schematic Reference

Hybrid Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Drive Motor Generator Control Module Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

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 (Symptom Related Diagnostic Procedures) 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.

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 (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 (LAT) (Cooling Fan Inoperative)Cooling Fan Inoperative (LE5) (Cooling Fan Inoperative)Cooling Fan Inoperative (LCS) (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 (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.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for APM replacement, setup, and programming