The engine control module (ECM) monitors the deviation of the voltage across the battery pack, using the 3 module voltage sensors. If one module within the battery pack is not within the expected value, it will manifest itself in a high Delta V SOH (state of health).

The engine is running.

Maximum module voltage - minimum module voltage is greater than 0.75 volts for 6 seconds.

The hybrid system is disabled.

Module voltage deviation returns to less than or equal to 0.75 volts.

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

Observe the scan tool BECM Hybrid Battery 1, Hybrid Battery 2 and Hybrid Battery 3 parameters while road testing the vehicle. The voltage difference between the battery voltages should be within 0.75 volts.

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.
2. Measure the voltage of each battery module, the voltages should be within 1.0 volt.

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

3. Disconnect harness connector X1 from the BECM. Refer to Hybrid Battery Service Disconnect/Connect.
4. 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.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.