* 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. Disconnect the harness connector at the current sensor.
3. Ignition OFF and scan tool disconnected for 30 seconds, test for less than 5 ohm between the low reference circuit terminal 2 and ground.
锟斤拷If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the drive
motor generator battery control module.
4. Connect the 12 V battery.
5. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.
锟斤拷If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the drive
motor generator battery control module.
锟斤拷If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the drive motor generator
battery control module.
6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 2. Verify the scan tool Calc.
Hybrid Batt. Current is greater than +225 A.
锟斤拷If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace
the drive motor generator battery control module.
7. If all circuits test normal, replace the current sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the repair.
* Drive Motor Battery Current Sensor Replacement ()
* Drive Motor Battery Sensor Module Wiring Harness Replacement ()
* Control Module References (See: Testing and Inspection/Programming and Relearning) for drive motor generator battery control module
replacement, setup and programming
P1A8A
DTC P1A8A
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P1A8A
- 42 Volt System Voltage High
Circuit/System Description
The Accessory Power Module (APM) supplies the energy that flows between the high voltage, 300 volt, direct current (DC) and intermediate
voltage, 42 volt, DC to support the Electric Power Steering (EPS). The APM receives a 42 volt enable command from the Hybrid Powertrain
Control Module (HPCM) over the high speed hybrid GMLAN communication circuit. 42 volt APM functions will run only when the 42 volt APM
enable is active on the high speed hybrid GMLAN communication circuit.
Conditions for Running the DTC
APM 42 volt output commanded on.
Conditions for Setting the DTC
APM 42 volt circuit above 50 volts for more than 3 seconds.
