P1A0C

DTC P1A0C or P1A0D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptors
DTC P1A0C
- Battery Energy Control Module System Voltage Low

DTC P1A0D
- Battery Energy Control Module System Voltage High




Circuit/System Description

The battery energy control module (BECM) monitors the system voltage for a high or low condition.


Conditions for Running the DTC

The engine is running.


Conditions for Setting the DTC

P1A0C

System voltage is less than the system voltage lower threshold of 6 volts for 3 seconds.

P1A0D

System voltage is greater than the system voltage upper threshold of 18 volts for 3 seconds.


Action Taken When the DTC Sets

P1A0C

Hybrid system is disabled.

P1A0D

Does not affect hybrid operation.


Conditions for Clearing the DTC

System voltage returns to between 11-18 volts.


Reference Information
Schematic Reference

Hybrid Energy Storage Schematics ()
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

J 35616 GM Approved Terminal Test Kit


Circuit/System Testing

Caution: To help avoid personal injury, additional precautions must be taken prior to working on the generator control module or the generator starter. After removing the 36V battery cables from the generator battery, remove both engine wiring harness connectors from the generator control module. Wait at least 5 minutes and then remove the generator control module cover. Verify voltage levels at all 36V, 12V, and 3-phase connections, are less than 3 volts using a DMM before proceeding.


Caution: To help avoid personal injury, be careful when working in the vicinity of the generator battery disconnect control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.


Important: In order to avoid damaging BECM X1 and X2 connector terminals, the proper test probes should be used. The proper test probes are as follows:



* J-35616-65B for female terminals
* J-35616-64B for male terminals


1. Verify the DTC is set as current.

• If the DTC is history, refer to Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics).

2. Disconnect harness connector X2 for the BECM. Refer to Hybrid Battery Service Disconnect/Connect ().
3. Ignition OFF, verify that there is less than 2.0 ohms between the ground circuits X2 terminals 12-13 and ground.

• If greater than the specified value, test the ground circuits for an open/high resistance.

4. Ignition ON, observe and record the scan tool ECM ignition signal parameter.
5. Ignition ON, measure the between the BECM ignition 1 voltage circuit X2 terminal 16 and the ground circuit of the BECM.

• If the ECM parameter and the measured BECM ignition 1 voltage circuit differ by more than 2 volts, test the ignition 1 voltage circuit for a short to ground or an open/high resistance.

6. If the circuit test normal, replace the BECM.
7. Engine running, observe and record the scan tool ECM ignition signal parameter.
8. Engine running, measure the between the ignition 1 voltage circuit X2 terminal 16 and the ground circuits of the BECM.

• If the ECM parameter and the measured BECM ignition 1 voltage circuit differ by more than 2 volts, replace the BECM.




Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning) for BECM replacement, setup, and programming