P0BC1
DTC P0A81 or P0BC1
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0A81
- Hybrid Battery Pack Cooling Fan Control Circuit
DTC P0BC1
- Hybrid Battery Pack Cooling Fan Positive Voltage Control Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
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 drive motor generator battery control module (BECM) supplies a ground to the battery vent fan relay. A ground wire from the battery vent fan motor assembly completes the path to case ground. A 5 V circuit is provided from the battery vent fan motor assembly, to the drive motor generator battery control module. The drive motor generator battery control module uses a pulse width modulated (PWM) signal on the 5 V circuit to control the battery vent fan motor duty cycle. The drive motor generator battery control module uses 4 battery temperature sensors, one air inlet duct and one air outlet temperature sensor to control battery vent fan motor operation and speed.
Conditions for Running the DTC
P0A81
* The ignition is ON.
* Battery voltage is 9-18 V.
* The fan speed is commanded 35 percent or greater.
P0BC1
* The ignition is ON.
* Battery voltage is 9-18 V.
* The fan has transitioned from either ON to OFF or from OFF to ON.
Conditions for Setting the DTC
P0A81
Fan control signal monitor voltage to the drive motor generator battery control module is greater than 2.3 V or less than 0.5 V for 5 seconds.
P0BC1
The fan speed control circuit is greater than 0.9 V for 1 second.
Action Taken When the DTC Sets
DTCs P0A81 and P0BC1 are type B DTCs.
Conditions for Clearing the DTC
DTCs P0A81 and P0BC1 are type B DTCs.
Diagnostic Aids
Inspect the blower motor for foreign materials and obstuctions that can cause a DTC P0A81.
Reference Information
Schematic Reference
Hybrid Cooling Schematics Hybrid Cooling Schematics
Connector End View Reference
Component Connector End Views Connector Views
Description and Operation
Drive Motor Battery Cooling Description Drive Motor Battery Cooling Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Special Tools
EL-48900 HEV Safety Kit
Circuit/System Verification
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 after approximately a 10 second delay.
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.
Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:
* Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors.
* Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors.
- Visually and functionally inspect the gloves before use.
- Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not.
Failure to follow the procedures exactly as written may result in serious injury or death.
Note: Perform the Generator Battery Vent Fan test first
Generator Battery Vent Fan Test
1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling High Voltage Disabling.
2. Ignition OFF, disconnect the generator battery vent fan.
3. Connect the 12 V battery.
4. Test for less than 5 ohm between the generator battery vent fan ground circuit terminal 3 and ground
• If greater than the specified range, test the ground circuit for an open/high resistance.
5. Connect a test lamp between the control circuit terminal 2 and the ground circuit terminal 3.
6. Command the battery pack vent fan speed between 0 and 60 percent with a scan tool. The test lamp should turn ON and OFF after a 10 second delay.
• If the test lamp does not turn ON and OFF, refer to Generator Battery Vent Fan Relay test.
7. Connect a DMM between the control circuit terminal 4 and ground.
8. Command the battery vent fan to 60 percent with a scan tool. Test for less than 1 V after a 10 second delay.
• If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the drive motor generator battery control module.
9. Command the battery vent fan to 0 percent with a scan tool. Switch the DMM to the diode test. The DMM reading should display O.L.
• If less than the specified value, test the control circuit for a short to ground. If the circuits test normal, replace the drive motor generator battery control module.
10. Command the battery vent fan to 60 percent with a scan tool. The reading should be less than 3 V.
• If less than the specified range or displaying O.L., test the control circuit for an open/high resistance. If the circuits test normal, replace the drive motor generator battery control module.
Generator Battery Vent Fan Relay Test
1. Disconnect the harness connector at the battery vent fan relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 4 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 4 for a short to ground. If the circuit tests normal, replace the battery vent fan relay.
4. Verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.
• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Connect a 15 A fused jumper wire between the B+ circuit terminal 3 and the control circuit terminal 4. Verify the generator battery vent fan is activated.
• If the cooling fan does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the generator battery vent fan.
6. Connect a test lamp between the B+ circuit terminal 2 and the control circuit terminal 1.
7. Command the battery pack vent fan speed between 0 and 60 percent with a scan tool. The test lamp should turn ON and OFF after a 10 second delay.
• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the drive motor generator battery control module.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the drive motor generator battery control module.
8. If all circuits test normal, test or replace the generator battery vent fan relay.
Component 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.
Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:
* Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors.
* Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors.
- Visually and functionally inspect the gloves before use.
- Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not.
Failure to follow the procedures exactly as written may result in serious injury or death.
Fan Relay Test
1. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling High Voltage Disabling.
2. Ignition OFF, disconnect the drive motor generator battery vent fan relay.
3. Test for 85-110 ohm between terminals 1 and 2.
• If not within the specified range, replace the relay.
4. Test for infinite resistance between the following terminals:
* 1 and 3
* 1 and 4
* 2 and 3
* 2 and 4
* 3 and 4
• If not the specified value, replace the relay.
5. Install a 5 A fused jumper wire between relay terminal 2 and 12 V. Install a jumper wire between relay terminal 1 and ground. Test for less than 2 ohm between terminals 3 and 4.
• If greater than the specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Drive Motor Battery Control Module Harness Replacement Drive Motor Battery Control Module Harness Replacement
* Generator Battery Vent Fan Replacement Generator Battery Vent Fan Replacement
* Generator Battery Vent Fan Relay Replacement Generator Battery Vent Fan Relay Replacement
* Control Module References Control Module References for drive motor generator battery control module replacement, setup, and programming