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
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Accessory voltage is 9-18 volts, vehicle power mode is RUN Parameter Normal Range: 14.5 volts | |||
Control Module Voltage Supply Circuit | 0 volts | 0 volts | -- |
Circuit/System Description
The drive motor generator battery control module is also referred to as the battery energy control module (BECM). The BECM will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is communicated from the BECM to the hybrid powertrain control module (HPCM) through the Hybrid LAN communication circuit. The HPCM is the host controller for diagnostic trouble code (DTC) information.
The BECM continuously monitors the system voltage on the ignition 1 voltage circuit. Low or higher than normal ignition voltage may be inadequate for operation of the energy storage components. Improper operation may cause erratic hybrid drive motor battery operation that could include a no start condition. A system over voltage longer than 8 minutes will cause the HV contactor relay coils to get hot. The BECM will send a message to the HPCM to open the contactor relays. The HPCM will open the high voltage contactor relays when vehicle speed is below a calibrated value not close them for 30 minutes in order to allow the contactor relays to cool.
Conditions for Running the DTC
| • | The vehicle power mode is RUN. |
| • | DTC P0A1F is not set. |
Conditions for Setting the DTC
P1A0C
The BECM detects the ignition voltage is less than 9 volts for 3 seconds.
P1A0D
The BECM detects the ignition voltage is greater than 16 volts for 3 seconds.
Action Taken When the DTC Sets
P1A0C and P1A0D
| • | The BECM commands the battery vent fan to High. |
| • | DTCs P1A0C and P1A0D are Type C DTCs. |
P1A0D Only
After 8 minutes of ignition voltage over 16 volts, the HV contactor relay coils will become hot and the BECM will send a message to the HPCM. The HPCM will open the HV contactor relays when conditions allow, and not close them for 30 minutes in order to allow HV contactor relays to cool.
Conditions for Clearing the DTC
| • | The control module ignition voltage is between 9-16 volts. |
| • | DTCs P1A0C and P1A0D are Type C DTCs. |
Diagnostic Aids
Observe the driver information center (DIC) messaging that would indicate the charging system requires service.
Inspect for the following conditions:
| • | Loose or poor connections at the hybrid drive motor battery X350 18-way connector. |
| • | Verify that the 12 volt battery and charging system is within normal operating range and if a battery charger was connected to the vehicle. |
| • | Loose or damaged battery terminals. |
| • | Loose or corroded connections at the accessory dc power control module (APM). |
Reference Information
Schematic Reference
Hybrid Energy Storage Schematics
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
EL-48900 HEV Safety Kit
Circuit/System Verification
- Ignition ON, engine running, with a scan tool, monitor the control module voltage parameter in the BECM data display list. The control module voltage should be between 12.0-15.5 volts.
- Operate the vehicle within the Conditions for Running the DTCs. You may also operate the vehicle within the conditions that you observed from the Freeze Fame/Failure Records data.
Circuit/System Testing
- Start the engine.
- Verify that DTCs P0A8D and P0A8E are not set.
- With a scan tool, monitor the control module voltage parameter in the BECM data display list. The voltage parameter should display between 12.0-15.5 volts.
| ⇒ | If the DTCs P0A8D and P0A8E are set, repair them first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
| ⇒ | If the voltage is less than the specified value, test the ignition voltage circuit for an open/high resistance connection, If all circuits test normal replace the drive motor generator battery control module. |
| ⇒ | If the voltage is more than the specified value, replace the drive motor generator battery control module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
Control Module References for drive motor generator battery control module replacement, setup, and programming
