2010 Cadillac Truck Escalade RWD V8-6.2L Page 1570
Important: Do not turn the ignition to START.
2. Turn the ignition key to the RUN position. Ensure that the high voltage contactor relays close. Do not go to START.
瀚慖f the high voltage contactor relays do not close, diagnose the DTC or symptom that is preventing them from closing before attempting to
diagnose this DTC.
3. Test for DTC P1A88.
瀚慖f the diagnostic is set as Last Test Failed/Current, replace the APM.
4. Start the engine.
5. Test for DTCs P1A89, P1A8A and P1A8C.
瀚慖f any of the above diagnostics are set, diagnose those first.
6. After the engine has started, retest for DTC P1A88.
瀚慖f the diagnostic is set as Last Test Failed/Current, proceed to Circuit/System Testing.
瀚慖f the diagnostic is set as Last Test Passed, the external condition that set this DTC is no longer present. Clear the DTC Information. No
further diagnosis of this DTC is required.
Circuit/System Testing
Important: Perform Circuit/System Verification prior to performing Circuit/System Testing.
1. Turn the ignition key to the OFF position.
2. Disconnect the 42 volt X2 harness connector at the APM.
3. Turn the ignition key to ON. Do not go to START.
4. Use the scan tool APM Intermediate Voltage Control under the APM special functions list to turn on the 42 volt circuit.
瀚慖f the APM Intermediate Voltage is not between 40 and 44 volts, replace the APM.
瀚慖f the APM Intermediate Voltage is between 40 and 44 volts, the problem is not in the APM. This DTC can set for the following external
reasons:
* High voltage contactor relays opening any time the APM is doing 42 volt conversion.
* The high voltage system is greater than 390 volts or less than 216 volts during 42 volt conversion. Extreme cold weather conditions may
occasionally cause the high voltage system to be greater than 390 volts.
* The 12 volt circuit is less than 6.7 volts during 42 volt conversion.
* A short circuit condition on the 42 volt circuit which causes the APM to produce greater than 60 amps.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
Control Module References (See: Testing and Inspection/Programming and Relearning) for APM replacement, setup, and programming.
P1A89
DTC P1A89
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 P1A89
- 42 Volt System Voltage Low
Circuit/System Description
The Accessory Power Module (APM) supplies the energy that flows between the high voltage, 300 volt, direct current (DC) and intermediate
