Diagnostic Instructions
DTC Descriptors
DTC P1A25: Hybrid Battery 1 Voltage Performance
DTC P1A2C: Hybrid Battery 2 Voltage Performance
DTC P1A33: Hybrid Battery 3 Voltage Performance
Circuit/System Description
The battery energy control module (BECM) performs a rationality check for the module voltage sensor 1, 2, and 3. If the voltage is not valid, the appropriate DTC will set.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
P1A25
| • | Module Voltage 1 - Module Volts Average is greater than 6 volts. |
| • | Module Volts Average = (MIDDLE (ModVolt1, ModVolt2, ModVolt3) + (PackVoltage/3) + (PowerElectronicsVolt/3)/3. |
P1A2C
| • | Module Voltage 2 - Module Volts Average is greater than 6 volts. |
| • | Module Volts Average = (MIDDLE (ModVolt1, ModVolt2, ModVolt3) + (PackVoltage/3) + (PowerElectronicsVolt/3)/3. |
P1A33
| • | Module Voltage 3 - Module Volts Average is greater than 6 volts. |
| • | Module Volts Average = (MIDDLE (ModVolt1, ModVolt2, ModVolt3) + (PackVoltage/3) + (PowerElectronicsVolt/3)/3. |
Action Taken When the DTC Sets
The hybrid system is disabled.
Conditions for Clearing the DTC
| • | Module voltage deviation from average voltage is less than the threshold. |
| • | Pack voltage equals Valid. |
| • | System voltage 11-18 volts |
| • | Startup Timer is greater than 6 seconds. |
| • | The battery current is between -5 A and 5 A. |
Reference Information
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
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 |
- Scan and record the hybrid battery voltage parameters for modules 1, 2, and 3.
- Measure the module voltages 1, 2, and 3, DTC and compare it to the parameter scanned values in step 1. Refer to
Hybrid Battery Service Disconnect/Connect.
| ⇒ | If the module with the DTC has greater than 1 volt measured difference from the other 2 modules, replace the battery pack. |
- Disconnect harness connector X1 from the BECM.
- 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. |
- If all circuits test normal, replace the BECM.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
