2010 Cadillac Truck Escalade RWD V8-6.2L Page 1556
* 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 Descriptors
DTC P1A8B 00
- 42 Volt Inverter Temperature High
DTC P1A8B 11
- 42 Volt Inverter Temperature High
DTC P1A8C
- 42 Volt Inverter Overtemperature
Circuit/System Description
The Accessory Power Module (APM) controls the energy flowing 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. APM functions will run only when the APM Enable is active on the
high speed hybrid GMLAN communication circuit.
Heat is generated in the 42-volt APM circuit solely through the demand for use of the EPS. The Engine Control Module (ECM) measures the
temperature of the Power Electronics Cooling Loop and commands the flow of 2 electrical coolant pumps. The APM transfers heat in the 42-volt
circuit to the APM Heat Plate which is then dissipated at the Power Electronics Front End Heat Exchanger.
Based on the severity of an overheat condition in the 42-volt circuit, the APM will make decisions ranging from notification of an over temperature
condition to the EPS to completely shutting down the 42-volt power conversion.
Conditions for Running the DTC
APM 42-volt output commanded on.
Conditions for Setting the DTC
P1A8B 00
42-volt circuit temperature is greater than 105掳C (221掳F).
P1A8B 11
42-volt circuit temperature is greater than 115掳C (239掳F).
P1A8C
42-volt circuit temperature is greater than 125掳C (257掳F).
Action Taken When the DTC Sets
P1A8B
* DTC P1A8B is a Type C DTC.
* The HPCM stores the DTC information in memory when the diagnostic runs and fails.
P1A8C
* DTC P1A8C is a Type C DTCs.
* The HPCM stores the DTC information in memory when the diagnostic runs and fails.
* The APM will shut down 42-volt conversion.
Conditions for Clearing the DTC
P18AB
DTC P1A8B is a Type C DTC.
