GM Service Manual Online
For 1990-2009 cars only

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 P0A95: High Voltage Fuse

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Disconnect Lever High Voltage

--

P0A95*, P0ABC*, P1A20**

--

--

*DTC P0A95 and P0ABC will only set if the HV contactors are closed when the fuse opens.

**DTC P1A20 will set if the fuse is open when the ignition is turned ON.

Typical Scan Tool Data

Hybrid Battery 11

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON

Parameter Normal Range: 13-19 Volts

Disconnect Lever High Voltage

--

0 Volts

--

Circuit/System Description

The high voltage (HV) direct current (DC) voltage system is protected by a 125 A fuse. The fuse is located in the high voltage manual disconnect lever and can only be serviced by replacing the HV manual disconnect lever. The fuse is positioned between the negative and positive terminals at hybrid battery 11. If the fuse is open or the high voltage manual disconnect lever is removed, the scan tool parameter will display 0 Volts for hybrid battery 11. The drive motor generator battery control module (GBCM) monitors the high voltage interlock circuit (HVIC) for normal operation along with hybrid battery 11 voltage in order to determine if the high voltage fuse is open. If the fuse is open this could indicate that there may be a short between the positive and negative high voltage DC circuit. The high voltage system is isolated from chassis ground.

Conditions for Running the DTC

    • DTC P0A1F is not set.
    • The ignition is ON.
    • The HVIC is normal.
    • The HV contactors are closed.
    • The 12 V battery voltage is 9-18 V.

Conditions for Setting the DTC

All of the following conditions exist for 1 second:

    • Hybrid Battery 10 voltage is greater than 2 Volts.
    • Hybrid Battery 11 voltage is less than 2 Volts.
    • Hybrid Battery 12 voltage is greater than 2 Volts.

Action Taken When the DTC Sets

DTC P0A95 is a type C DTC.

Conditions for Clearing the DTC

DTC P0A95 will pass when the contactors are closed, and any of the following conditions exist for 1 second:

    • Hybrid Battery 10 voltage is less than 2 Volts.
    • Hybrid Battery 11 voltage is greater than 2 Volts.
    • Hybrid Battery 12 voltage is less than 2 Volts.

Diagnostic Aids

    • Avoid cycling the ignition unnecessarily while the fuse is open. Turning the ignition ON twice with an open fuse results in a 20-40 minute precharge wait time, during which time precharging will be inhibited. It will be necessary to wait until the scan tool Precharge Wait Time parameter counts down to 0 Seconds before continuing with diagnosis.
    • DTC P0A95 will only set if the fuse opens while the contactors are closed. If the fuse is already open when the ignition is turned from OFF to ON, the precharge test will fail, and DTC P1A20 will set.
    • When the high voltage fuse is open the vehicle will not start.
    • Test for HVIC circuit operation by lifting up on the high voltage manual disconnect lever to disengage the HVIC circuit. Monitor the HVIC source and return current on the scan tool. HVIC return current should read 0 ma when the high voltage manual disconnect lever is lifted.
    • If this DTC sets when the manual disconnect lever is removed, the HVIC circuit may have a wire to wire short on the HVIC source and return circuits between the X350 and the HV manual disconnect lever connector.
    • If the HV fuse opens as soon as the high voltage manual disconnect is installed with the ignition OFF and the HV contactor relays are not stuck closed, The problem is internal to the drive motor generator battery assembly.

Reference Information

Schematic Reference

    •  Hybrid Energy Storage Schematics
    •  Hybrid Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Drive Motor Battery System Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • EL-48458 HV Precharge Tester
    • EL-48569 Terminal Covers
    • EL-48900 HEV Safety Kit

Circuit/System Verification

Ignition ON, observe the scan tool Hybrid Battery 11 parameter. The reading should be between 13 and 19 Volts.

Circuit/System Testing

    Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.

    The High Voltage Disabling procedure will perform the following tasks:

       • Identify how to disable high voltage.
       • Identify how to test for the presence of high voltage.
       • Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
    Failure to follow the procedures exactly as written may result in serious injury or death.

  1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling.
  2. Test for infinite resistance between the HV terminals 1 X3 and 2 X3 of the manual disconnect lever, in order to verify that the fuse is open.
  3. If not the specified value, test the HVIC circuit for a wire to wire short on the HVIC source and return circuits between the X350 and the HV manual disconnect lever connector. Inspect the high voltage cables internal to the battery assembly for proper connections. If all circuits test normal, replace the drive motor generator battery assembly.
  4. Disconnect the X1 and X2 HV DC cables from the battery assembly.
  5. Visually inspect all HV DC cables for damage or conditions that may have caused them to short together. Inspect the high voltage cables between the drive motor generator battery and the drive motor generator control module, and between the drive motor generator control module and the air conditioning compressor.
  6. If any of the HV cables are damaged, replace the damaged HV DC cables.
  7. Connect the EL-48458 at the drive motor generator battery assembly. Refer to the EL-48458 installation procedure located in High Voltage System Diagnosis.
  8. Connect the 12 V battery. Refer to Battery Negative Cable Disconnection and Connection. Install a new HV manual disconnect lever.
  9. Ignition ON, attempt to precharge the HV system by moving the HV contactor relay switch on the tester to the closed position. Verify that the Hi-voltage circuit LED for Hi-voltage greater than 60 volts illuminates and stays illuminated. Wait 3 minutes. Verify the HV fuse does not open and that the precharge does not fail.
  10. If the fuse opened or if the precharge failed, inspect the HV cables inside the battery assembly for damage or conditions that may have caused them to short together. Repair or replace the drive motor generator battery assembly.
  11. Ignition OFF, disable the high voltage at the drive motor generator control module assembly. Refer to High Voltage Disabling.
  12. Disconnect the X4 and X5 air conditioning control module (ACCM) cables and the X2 and X3 HV DC cables from the power inverter module (PIM).
  13. With the HV DC cables disconnected from the battery assembly and at the PIM, test for infinite resistance between the HV+ circuit terminal X2 and HV- circuit terminal X3 of the HV DC cables.
  14. If less than the specified value, replace the HV DC cables.
  15. Connect the X2 and X3 HV DC cables to the PIM and the X1 and X2 HV DC cables to the battery assembly. Leave the X4 and X5 ACCM cables disconnected.
  16. Temporarily install the PIM high voltage distribution cover and drive motor generator control module sight shield.
  17. Connect the 12 V battery. Refer to Battery Negative Cable Disconnection and Connection.
  18. With the ACCM cables disconnected, install the HV manual disconnect lever. Start the engine, and operate the vehicle. Verify the HV fuse does not open and that the precharge does not fail.
  19. If the fuse opened or if the precharge failed, replace the drive motor generator control module.
  20. If all circuits test normal, replace the ACCM.

Component Testing

Manual Disconnect Lever Test

    Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.

    The High Voltage Disabling procedure will perform the following tasks:

       • Identify how to disable high voltage.
       • Identify how to test for the presence of high voltage.
       • Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
    Failure to follow the procedures exactly as written may result in serious injury or death.

  1. Remove the high voltage manual disconnect lever.
  2. Test for less than 1 Ω between terminals 1 X3 and 2 X3 of the disconnect lever.
  3. If greater than the specified value, replace the high voltage manual disconnect lever.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Drive Motor Battery 300-Volt Positive and Negative Cable Replacement
    •  Drive Motor Generator Battery Replacement
    •  Air Conditioning Compressor Replacement
    •  Control Module References - for drive motor generator battery control module, drive motor power inverter module, or accessory DC power control module replacement, setup, and programming.