GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 Yukon - 4WD 🢒 Hybrid 🢒 Hybrid Controls 🢒 DTC P0AF7

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions 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.

Conditions for Running the DTC

Ignition/Accessory On.

Conditions for Setting the DTC

APM heat plate temperature is greater than 105°C (221°F).

Action Taken When the DTC Sets
    • DTC P0AF7 is a Type C DTC.
    • The APM will shut down charging or Jump Assist.
    • The APM will also set DTC P1A8B 11 42-Volt Inverter Temperature High to limit power to the EPS.

Conditions for Clearing the DTC
    • DTC P0AF7 is a Type C DTC.
    • APM heat plate temperature is less than 95°C (203°F).

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 water pump.

Reference Information

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Review the Failure Records when the DTC set.
    2. ⇒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.

Circuit/System Testing
  1. Inspect for proper coolant level in the hybrid cooling system reservoir.
    2. ⇒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.
    3. ⇒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.
    4. ⇒If a concern is found, repair or replace the coolant pumps as necessary.
  4. Command the cooling fans through all operating speeds.
    5. ⇒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 .
    6. ⇒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 after completing the diagnostic procedure.

Control Module References for APM replacement, setup, and programming