Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Drive Motor Battery System Description ()
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (See: Diagnostic Trouble Code Descriptions/Powertrain Diagnostic Trouble Code
(DTC) Type Definitions)
Special Tools
EL-48900 HEV Safety Kit
Circuit/System Verification
Verify that P0C76 is not set.
If DTC is set, refer to High Voltage Contactor/Relay Malfunction ().
P0C77
DTC P0C77 or P1A20
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0C77
- Hybrid Battery System Precharge Time Too Short
DTC P1A20
- Hybrid Battery System Precharge Time Too Long
Circuit/System Description
The drive motor generator battery control module is also referred to as the battery energy control module (BECM). The drive motor generator
battery control module will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is
communicated from the drive motor generator battery control module to the hybrid powertrain control module (HPCM) through serial data. The
hybrid powertrain control module is the host controller for diagnostic trouble code (DTC) information.
The drive motor generator battery contains 3 high voltage contactors that allow the high voltage direct current (DC) batteries to be connected to the
vehicle or safely contain the DC high voltage within the drive motor generator battery assembly. The three contactor/relays are a positive high
voltage contactor, negative high voltage contactor, and the current limit relay.
The power-up sequence for the high voltage DC system occurs in the following order:
1. The drive motor generator battery control module performs a precharge test, by closing both the negative contactor and current limit relay.
Because the current limit relay routes the high voltage current through a current limit resistor, the hybrid battery terminal voltage should
increase at a steady, predictable rate.
2. When the drive motor generator battery control module observes that hybrid battery terminal voltage and hybrid battery calculated voltage
