Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P1A0C: Battery Energy Control Module System Voltage LowDTC 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.
Diagnostic Aids
| • | A high or low voltage value in multiple modules indicates a concern in the charging system. |
| • | Overcharging with a battery charger can cause this DTC to set. |
Reference Information
Schematic Reference
Hybrid Energy Storage Schematics
Connector End View Reference
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
Circuit/System Testing
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.
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.
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 |
- Verify the DTC is set as current.
- Disconnect harness connector X2 for the BECM. Refer to Hybrid Battery Service Disconnect/Connect.
- Ignition OFF, verify that there is less than 2.0 ohms between the ground circuits X2 terminals 12-13 and ground.
- Ignition ON, observe and record the scan tool ECM ignition signal parameter.
- Ignition ON, measure the between the BECM ignition 1 voltage circuit X2 terminal 16 and the ground circuit of the BECM.
- If the circuit test normal, replace the BECM.
- Engine running, observe and record the scan tool ECM ignition signal parameter.
- Engine running, measure the between the ignition 1 voltage circuit X2 terminal 16 and the ground circuits of the BECM.
| ⇒ | If the DTC is history, refer to Testing for Intermittent Conditions and Poor Connections. |
| ⇒ | If greater than the specified value, test the ground circuits for an open/high resistance. |
| ⇒ | 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. |
| ⇒ | 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 after completing the diagnostic procedure.
Control Module References for BECM replacement, setup, and programming
