2010 Cadillac Truck Escalade RWD V8-6.2L Page 1561
drive motor generator power inverter module, air conditioning control module assembly replacement, setup and programming
P1A21
DTC P1A21
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 P1A21
- Hybrid Battery Contactor Control Sequence Incorrect
Circuit/System Description
The drive motor generator battery control module is also referred to as the battery energy control module (BECM). The drive motor generator
battery control module will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is
communicated from the drive motor generator battery control module to the hybrid powertrain control module (HPCM) through serial data. The
hybrid powertrain control module is the host controller for diagnostic trouble code (DTC) information.
The hybrid powertrain control module controls the operation of the high voltage contactors through communication with the drive motor generator
battery control module. The hybrid powertrain control module utilizes a pulse width modulated (PWM) contactor system request circuit and
redundant serial data to command the high voltage contactors Open and Closed. Under normal operating conditions, the drive motor generator
battery control module opens and closes the high voltage contactors based only upon the hybrid powertrain control module command. This
diagnostic identifies when the drive motor generator battery control module has opened the high voltage contactors when the hybrid powertrain
control module is commanding them closed.
Conditions for Running the DTC
* The vehicle power mode is RUN.
* Ignition voltage is 9-18 V.
* The vehicle has passed a successful precharge and the high voltage contactors have been closed this ignition cycle.
* The hybrid powertrain control module is commanding the drive motor generator battery control module to keep the high voltage contactor
closed.
Conditions for Setting the DTC
The drive motor generator battery control module reports that the contactors are open when the hybrid powertrain control module contactor system
request circuit and the serial data message both indicate a closed request.
Action Taken When the DTC Sets
DTC P1A21 is a Type A DTC.
Conditions for Clearing the DTC
DTC P1A21 is a Type A DTC.
Diagnostic Aids
* The drive motor generator battery control module will set Contactor System Status parameter to OPEN when the Contactor System Request
Circuit Command parameter percent duty cycle is 65-75 percent.
* The drive motor generator battery control module will set Contactor System Status parameter to CLOSED when the Contactor System
Request Circuit Command parameter percent duty cycle is 25-35 percent.
Reference Information
Schematic Reference
Hybrid Energy Storage Schematics ()
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
