P0AF7

DTC P0AF7

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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 rises above 105°C (221°F).

Action Taken When the DTC Sets

* The Hybrid Control Module (HCM) stores the DTC information in memory when the diagnostic runs and fails.
* The APM will disable 14 volt power conversion.
* The APM will also set DTC P1A8B 11 42 Volt Inverter Temperature High to limit power to the EPS.

Conditions for Clearing the DTC

APM Heat Plate Temperature falls below 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.

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 - Cooling System and correct that concern first. Symptom Related Diagnostic Procedures

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.

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 (w/o LFA) Cooling Fan Inoperative (w/ LFA). 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.

Repair Instructions

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