P1B33
DTC P1B33-P1B39
Diagnostic Instructions
Danger: This diagnostic has NOT been validated on-vehicle. Follow all safety protocol and utilize all appropriate personal protective equipment to ensure your safety. Failure to follow the procedures exactly as written may result in serious injury or death.
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P1B33
- Battery Energy Control Module Hybrid Battery Voltage Balance Circuit
DTC P1B34
- Battery Energy Control Module Hybrid Battery Voltage Balance Processor 1 Performance
DTC P1B35
- Battery Energy Control Module Hybrid Battery Voltage Balance Processor 2 Performance
DTC P1B36
- Battery Energy Control Module Hybrid Battery Voltage Balance Processor 3 Performance
DTC P1B37
- Battery Energy Control Module Hybrid Battery Voltage Balance Processor 4 Performance
DTC P1B38
- Battery Energy Control Module Hybrid Battery Voltage Balance Processor 5 Performance
DTC P1B39
- Battery Energy Control Module Hybrid Battery Voltage Balance Processor 6 Performance
Circuit/System Description
The hybrid battery pack contains a total of 32 cell groups in the hybrid/EV battery pack assembly. These cell groups are electrically connected in series. Each individual cell group is rated at 3.7 V, for a nominal system voltage of 118 V DC. The battery cells are grouped together into two sections, each with 16 cell groups.
The battery energy control module monitors the voltage of the 32 battery cell groups. A voltage sense circuit is attached to each individual cell group. Each of these circuits terminate at a connector located on the top surface of the battery section. A serviceable auxiliary battery wiring harness connectors the voltage sense circuits to the battery energy control module, located directly above the hybrid battery pack.
To ensure proper battery function and lengthen battery life, the battery energy control module balances the voltage of the cells so that each cells maintains the same voltage level. The battery energy control module uses internal voltage gates to transfer voltage from cells with a higher voltage level to those cells with a lower voltage level. To maintain a similar state of charge on the cell groups, the starter/generator control module monitors the cell voltages and determines which cells need energy removed in order to maintain the cells at a similar state of charge. A resistor wired in parallel with the cell and a transistor switch in series with the resistor internal to the battery energy control module. The starter/generator control module sends a command to the battery energy control module to begin cell balancing.
Conditions for Running the DTC
DTC P1B33
* Battery voltage is greater than 8.8 V
* Battery energy control module is awake and communicating
* Internal cell balancing is not in progress
DTC P1B34, P1B35, P1B36, P1B37, P1B38, P1B39
* Battery voltage is greater than 9.6 V
* Battery energy control module is awake and communicating
Conditions for Setting the DTC
DTC P1B33
The balancing switch status does not equal the balancing switch command
DTC P1B34, P1B35, P1B36, P1B37, P1B38, P1B39
An internal communication fault has occurred within the battery energy control module
Action Taken When the DTC Sets
* DTCs P1B33, P1B34, P1B35, P1B36, P1B37, P1B38, and P1B39 are type B DTCs
* The vehicle operates in a low battery mode with the high voltage contactors closed, but no hybrid functions will occur
Conditions for Clearing the DTC
DTCs P1B33, P1B34, P1B35, P1B36, P1B37, P1B38, and P1B39 are type B DTCs
Reference Information
Schematic Reference
Hybrid Energy Storage Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Drive Motor Battery System Description Drive Motor Battery System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Special Tools
EL-48900 - HEV Safety Kit
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Verification
Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
The High Voltage Disabling procedure will perform the following tasks:
* Identify how to disable high voltage.
* Identify how to test for the presence of high voltage.
* Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:
* Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors.
* Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors.
- Visually and functionally inspect the gloves before use.
- Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not.
Failure to follow the procedures exactly as written may result in serious injury or death.
Danger: The eAssist battery pack assembly will utilize an exchange program. Please consult the most recent revision of bulletin/PI #PIPXXYYZZ, available in Service Information (SI), for a list of approved eAssist battery pack assembly service procedures. Components that may be removed and serviced without exchanging the complete battery pack assembly are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.
1. Verify that DTC P1B33, P1B34, P1B35, P1B36, P1B37, P1B38, or P1B39 is not set.
• If any of the DTCs are set, replace the K16 battery energy control module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module References for battery energy control module replacement, programming and setup