The battery energy control module (BECM) monitors the hybrid battery system for an overvoltage condition. A diagnostic is running continuously to verify that the battery pack voltage is not above 52 volts. DTC P1A4E will set if the diagnostic detects that the voltage is above 52 volts.

The ignition is in the RUN position.

Hybrid battery pack voltage greater than 52 volts.

Does not affect hybrid system operation

Hybrid battery pack voltage returns to normal operating range.

Schematic Reference

Hybrid Energy Storage Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Generator Battery Carrier Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 35616 GM Approved Terminal Test Kit

Warning: 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.

Warning: 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.

Note:  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:

1. Verify the DTC is set as current.

⇒	If the DTC is history, refer to Testing for Intermittent Conditions and Poor Connections.

2. Scan and record the hybrid battery pack voltage.
3. Measure the voltage between ring terminal 3 and ground. Should read less than 52 volts. Refer to Hybrid Battery Service Disconnect/Connect.

⇒	If greater than the specified value, replace the battery pack.

4. Disconnect harness connector X1 from the BECM.
5. Test for 1.3-1.7k ohms between the following circuits:

•	X1 terminal 1 to Generator Battery 1-X1

•	X1 terminal 11 to Generator Battery 1-X2

•	X1 terminal 2 to Generator Battery 2-X2

•	X1 terminal 12 to Generator Battery 3-X2

⇒	If not within specified range, replace the voltage sensor harness assembly.

6. If all circuits test normal, replace the BECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.