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 is greater than 2.3 volts or less than 0.5 volt for 5 seconds.

DTC P0A81 is a Type B DTC.

DTC P0A81 is a Type B DTC.

Verify the BECM fan fuse is not open.

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, observe the DTC information with a scan tool. DTC P0A81 should not set.
2. Ignition ON, command the battery pack vent fan speed to 60 percent duty cycle with a scan tool. The battery pack vent fan should turn ON.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. 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. Disconnect the harness connector at the battery vent fan motor.
5. Connect a test lamp between the ignition circuit terminal 2 and ground.
6. Ignition ON, command the battery pack vent fan speed to 60 percent. The test lamp should illuminate after a 5-7 second delay.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

7. Verify a test lamp illuminates between B+ and the ground circuit terminal 3.

⇒	If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

8. Ignition OFF, connect the harness connector at the battery vent fan motor.
9. Disconnect X2 harness connector at the BECM.
10. Verify a test lamp illuminates between the vent fan relay control circuit terminal 7 and ground.

⇒	If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the generator battery vent fan relay.

11. Connect a 3A fused jumper wire between the vent fan motor relay control circuit terminal 7 and ground.
12. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 2 and ground.

⇒	If the voltage is not within the specified range, test the signal circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the generator battery vent fan.

13. If all circuits test normal, replace the drive motor generator battery control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.