The generator battery disconnect control module monitors the system voltage for a high or low condition.

The engine is running.

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.

System voltage returns to a normal operating range.

Schematic Reference

Hybrid Energy Storage Schematics

Connector End View Reference

Hybrid Energy Storage Connector End Views

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

Special Tools

J 35616 GM Approved Terminal Test Kit

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 the generator battery disconnect control module C1 and C2 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. Disconnect harness connector C2 at the generator battery disconnect control module. Refer to Hybrid Battery Service Disconnect/Connect
3. Ignition OFF, verify that there is less than 2.0 ohms between the ground circuits C2 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 generator battery disconnect control module Ignition voltage circuit C2 terminal 16 and the ground circuit of the generator battery disconnect control module

⇒	If the ECM parameter and the measured generator battery disconnect control module Ignition voltage circuit differ by more than 2 volts, test the Ignition voltage circuit for a short to ground or an open/high resistance.

6. If the circuit test normal, replace the generator battery disconnect control module.
7. Engine running, observe and record the scan tool ECM Ignition signal parameter.
8. Engine running, measure the between the Ignition voltage circuit C2 terminal 16 and the ground circuits of the generator battery disconnect control module.

⇒	If the ECM parameter and the measured generator battery disconnect control module Ignition voltage circuit differ by more than 2 volts, replace the generator battery disconnect control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for generator battery disconnect control module replacement, setup, and programming