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 drive motor generator battery is cooled by a drive motor battery vent fan motor. The battery vent fan motor and battery vent fan relay are located inside the drive motor generator battery assembly. B+ to the battery vent fan is provided from the battery vent fan relay when the BECM supplies a ground to the battery vent fan relay. A grounding wire from the battery vent fan motor assembly completes the path to case ground. A 5-volt circuit is provided from the battery vent fan motor assembly, to the BECM. The BECM uses a pulse width modulated (PWM) signal on the 5 volt circuit to control the battery vent fan motor duty cycle. The battery vent fan motor also supplies an additional 5 volt signal that indicates vent fan speed back to the BECM, the lower the voltage the greater the fan speed. The BECM uses 4 battery temperature sensors, one air inlet duct and one air outlet temperature sensor to control battery vent fan motor operation and speed.

Fan control signal monitor voltage to BECM greater than 0.9 volt for 1 second.

DTC P0BC1 is a Type B DTC.

DTC P0BC1 is a Type B DTC.

Schematic Reference

Hybrid Energy Storage Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-48900 HEV Safety Kit

1. Ignition ON, engine OFF, with scan tool, command the battery pack vent fan speed to 60 percent duty cycle. The battery vent fan should turn ON and run at a medium-high speed.
2. 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 frame/failure records data.

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.

Failure to follow the procedures exactly as written may result in serious injury or death.
1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling .
2. Remove the drive motor generator battery case upper cover, front cover, and right side cover. Refer to Drive Motor Battery Case Upper Cover, Front Cover, and Right Side Cover Replacement .
3. Ignition OFF, connect the 12-volt battery.
4. Ignition ON, disconnect the X2 connector at the BECM, connect a DMM between terminal 2 and ground at the X2 harness connector. You should measure less than 0.9 volt.

⇒	If less than 0.9 volt, replace the drive motor generator battery control module.

5. Disconnect the harness connector at the vent fan relay.
6. Ignition OFF, connect a test lamp at the vent fan relay harness connector between terminals 1 and 2. The test lamp should not illuminate.

⇒	If the test lamp illuminates, test the vent fan relay control circuit for a short to ground. If the circuit tests normal, replace the drive motor generator battery control module.

7. Ignition ON, connect a test lamp at the vent fan relay harness connector terminal 4 and ground. The test lamp should not illuminate.

⇒	If the test lamp illuminates, repair the short to B+ on the supply voltage circuit between the battery fan relay and the battery vent motor.

8. Ignition OFF, disconnect the inline harness connector at the drive motor generator battery vent fan.
9. Ignition ON, connect a test lamp at the battery vent fan harness connector terminal 4. The test lamp should not illuminate.

⇒	If the test lamp illuminates, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the drive motor generator battery control module.

10. Test for infinite resistance between terminal 3 and 4 on the drive motor generator battery vent fan relay.

⇒	If continuity is detected, replace the drive motor generator battery vent fan relay.

⇒	If infinite resistance is measured, replace the drive motor generator battery vent fan.

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.

Failure to follow the procedures exactly as written may result in serious injury or death.
1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling .
2. Ignition OFF, disconnect the drive motor generator battery vent fan relay.
3. Test for 85-110 ohms across terminal 1 and terminal 2 on the vent fan relay.

⇒	If the resistance is not within the specified range, replace the drive motor generator battery vent fan relay.

4. Test for infinite resistance between terminals 3 and 4 on the vent fan relay. If continuity is detected, replace the drive motor generator battery vent fan relay.

Perform the Diagnostic Repair Verification after completing the repair.