P0A81
DTC P0A81
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P0A81
- Drive Motor Battery Fan Unit Failure
Typical Scan Tool Data
Circuit/System Description
The drive motor generator battery is cooled by a vent fan motor. The vent fan motor and vent fan motor relay are located inside the drive motor battery assembly. B+ to the vent fan is provided from vent fan relay when the battery energy control module (BECM) supplies a ground to the relay. A grounding wire from the vent fan motor assembly completes the path to ground. A 5-volt circuit is provided from the vent fan motor assembly, to the BECM. The BECM uses a pulsed width modulated (PWM) signal on the 5 volt circuit to control the vent fan motor duty cycle. The BECM uses 4 battery temperature sensors, one air inlet duct and one air outlet temperature sensor to control vent fan motor operation and speed.
Conditions for Running the DTC
* The vehicle power mode is RUN.
* Accessory voltage is 9-18 volts.
Conditions for Setting the DTC
* Fan speed commanded on at 35 percent or higher.
* Fan control signal monitor voltage to BECM is greater than 2.3 volts or less than 0.5 volts.
Action Taken When the DTC Sets
DTC P0A81 is a Type B DTC.
Conditions for Clearing the DTC
DTC P0A81 is a Type B DTC.
Diagnostic Aids
Check the BECM fan fuse.
Special Tools
EL-489000 HEV Safety Kit
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. DTC P0BC1 should not set.
^ If DTC P0BC1 is set, refer to DTC P0BC1. P0BC1
2. Ignition ON, command the battery vent fan motor to 80 percent duty cycle with a scan tool. The battery 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.
Circuit/System Testing
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.
Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling.
1. Remove the drive motor generator battery case upper cover, front cover, and right side cover.
2. Ignition OFF, connect the 12 volt battery.
3. Disconnect the harness connector at the battery vent fan motor.
4. Connect a test lamp between the ignition circuit terminal 2 and ground.
5. Ignition ON, command the drive motor generator vent fan relay ON. 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.
6. 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.
7. Ignition OFF, connect the harness connector at the battery vent fan motor.
8. Disconnect X2 harness connector at the BECM.
9. 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 battery vent fan relay.
10. Connect a 20A fused jumper wire between the vent fan motor relay control circuit terminal 7 and ground.
11. 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 battery vent fan motor.
12. If all circuits test normal, replace the BECM.
Repair Verification
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Generator Battery Vent Fan Replacement
* Drive Motor Generator Battery Control Module and Bracket Replacement