P0AFF
DTC P0AFF
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 P0AFF
- System Voltage Too Low For Voltage Step Down Conversion
Diagnostic Fault Information
Circuit/System Description
The accessory power module (APM) monitors its 14V circuit when it is enabled for Normal mode or Jump Assist. It requires a minimum voltage on this circuit in order to begin operation. This DTC sets when the 14V circuit in the APM is below this minimum level at the time it is enabled. APM functions will run only when an APM enable message from the hybrid powertrain control module (HPCM) is active on the high speed hybrid GMLAN communication circuit.
Conditions for Running the DTC
APM commanded to begin Normal mode or Jump Assist.
Conditions for Setting the DTC
14V circuit at the APM is below 7.0V when attempting to enter Normal mode or Jump Assist.
Action Taken When the DTC Sets
* DTC P0AFF is a Type C DTC.
* The HPCM stores the DTC information in memory when the diagnostic runs and fails.
* The APM will not allow 14V conversion.
Conditions for Clearing the DTC
* DTC P0AFF is a Type C DTC.
* The 14V circuit at the APM rises above 7.0 volts.
Diagnostic Aids
The APM is protected from reverse polarity connections by a 200-amp in-line mega-fuse. The output current of the APM is lower than the fuse rating.
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. Start the Engine.
2. Check for any other DTCs.
Circuit/System Testing
1. Remove the B+ harness connector X3 at the APM.
2. Connect a test lamp between the 12V battery positive and the APM connector X3 at the module.
3. Ignition ON, observe the 12V Circuit Voltage parameter in the APM data list. The parameter should be within 0.5V of the actual 12V battery voltage.
• If the voltage is not within the specified range, replace the APM.
• If the voltage is within the specified range, repair the high resistance condition in the 12V circuit.
Component Testing
1. Use APM Output Device Control to verify APM operation.
2. Turn the Ignition to ON.
3. Connect a DMM to the 12V battery.
4. Use the Device Control "APM set point control" to turn on the APM 14V system.
5. Vary the voltage setpoint with the scan tool ensuring that the DMM tracks the commanded voltage.
• If the APM set point control fails, replace the APM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* 200 Amp Mega Fuse and Auxiliary Electrical Center 12VDC Junction Block Replacement
* 12V Cable Replacement (Mega Fuse to APM)
* Control Module References (Programming and Relearning) for APM replacement, setup, and programming