P0AFF
DTC P0AFF
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) 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 14-volt circuit when it is enabled for charge or Jump Assist. It requires a minimum voltage on this circuit in order to begin operation. This DTC sets when the 14-volt 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 charging or Jump Assist.
Conditions for Setting the DTC
14-volt circuit at the APM is below 6.7 volts when attempting to begin charging or Jump Assist.
Action Taken When the DTC Sets
* DTC P0AFF is a Type C DTC.
* The APM will not allow 14-volt or 42-volt conversions to begin in this condition.
Conditions for Clearing the DTC
* DTC P0AFF is a Type C DTC.
* The 14-volt circuit at the APM is above 6.7 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 (Circuit Testing)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Testing
1. Remove the B+ harness connector X3 at the APM.
2. Connect a test lamp between the 12-volt battery positive and the APM connector X3 at the module.
3. Ignition ON, observe the 12-volt parameter in the APM data list. The parameter should be within 0.5 volt of the actual 12-volt battery voltage.
• If the voltage is not within the specified range, replace the APM.
4. Ignition OFF, Remove the positive connection at the 12-volt battery.
5. Measure the resistance between the X3 connector and the battery positive connection.
• If the resistance is greater than 1.0 ohm, repair the high resistance condition in the 12-volt circuit.
• If the resistance is less than 1.0 ohm, replace the battery positive cable - control module to auxiliary BEC.
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 (200 Amp Mega Fuse and Auxiliary Electrical Center 12VDC Junction Block Replacement)
* Battery Positive Cable Replacement (12V Battery to Auxiliary BEC) (Battery Positive Cable Replacement (12V Battery to Auxiliary BEC))Battery Positive Cable Replacement (Control Module to Auxiliary BEC) (Battery Positive Cable Replacement (Control Module to Auxiliary BEC))
* Control Module References (Programming and Relearning) for APM replacement, setup, and programming