2010 Cadillac Truck Escalade RWD V8-6.2L Page 1529
P1AF6
DTC P1AF4-P1AF7
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 P1AF4
- Drive Motor 1 Control Module Hybrid Battery Voltage Isolation Sensor Circuit Low Voltage
DTC P1AF5
- Drive Motor 1 Control Module Hybrid Battery Voltage Isolation Sensor Circuit High Voltage
DTC P1AF6
- Drive Motor 2 Control Module Hybrid Battery Voltage Isolation Sensor Circuit Low Voltage
DTC P1AF7
- Drive Motor 2 Control Module Hybrid Battery Voltage Isolation Sensor Circuit High Voltage
Circuit/System Description
The drive motor generator power inverter control module (PIM) contains two motor control modules (MCMs). Each MCM measures hybrid battery
high voltage (HV) with several internal sensors. The MCMs test for loss of isolation (LOI) between either the HV positive circuit or HV negative
circuit and vehicle chassis. The MCMs test for isolation when the HV contactor relays are closed. The battery energy control module (BECM) only
tests the hybrid battery assembly for HV loss of isolation when the HV contactor relays are open.
MCM LOI is detected through the use of two high-impedance resistors and voltage measuring circuitry. The two resistors are connected in series
between the HV positive and HV negative circuits. The center connection of the two resistors is also connected to vehicle chassis. The MCM then
measures the voltage drop across one of the resistors. Without a loss of isolation, the MCM should measure about half of the high voltage potential.
This is referred to as mid-pack voltage. The Mid-pack voltage value is then doubled by the software and displayed on a scan tool as Motor 1
Isolation Voltage or Motor 2 Isolation Voltage. When a loss of isolation is present, the motor isolation voltage display will indicate voltage that is
more or less than actual hybrid battery high voltage. The MCM monitors the LOI voltage measuring circuitry for correct operation.
Conditions for Running the DTC
* The control module runs the program to detect an internal fault when the key is ON.
* Ignition voltage is 8-18 volts.
Conditions for Setting the DTC
P1AF4 and P1AF6
The motor control module (MCM) detects isolation sensor voltage less than 0V.
P1AF5 and P1AF7
The MCM detects isolation sensor voltage greater than 564V.
Action Taken When the DTC Sets
* DTCs P1AF4, P1AF5, P1AF6 and P1AF7 are Type B DTCs.
* The hybrid powertrain control module (HPCM) commands the battery energy control module (BECM) to open the high voltage contactor
relays.
Conditions for Clearing the DTC
DTCs P1AF4, P1AF5, P1AF6 and P1AF7 are Type B DTCs.
