P0A81
DTC P0A81
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC P0A81
- Hybrid Battery Pack Cooling Fan Control Circuit / Open
Typical Scan Tool Data
Circuit/System Description
The drive motor generator battery control module will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is communicated from the drive motor generator battery control module to the drive motor generator control module through serial data. The drive motor generator control module is the host controller for diagnostic trouble code (DTC) information.
Drive motor generator battery is cooled by the drive motor battery coolant fan / drive motor battery coolant pump and a radiator. The drive motor battery coolant fan / drive motor battery coolant pump are located inside the drive motor generator battery assembly and are serviced as a complete cooler assembly. B+ to the drive motor battery coolant fan / coolant pump is provided by the drive motor generator battery control module from a high side driver. A grounding wire from the battery vent fan motor assembly completes the path to ground. A 5 V circuit is provided from the drive motor battery coolant fan, 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 drive motor battery coolant fan duty cycle. The drive motor battery coolant fan also supplies an additional 5 V signal that indicates fan speed feedback to the drive motor generator battery control module, the lower the voltage the greater the fan speed. The drive motor generator battery control module uses 4 battery temperature sensors, one air inlet duct and a coolant temperature sensor to control the drive motor battery coolant fan and pump operation.
Conditions for Running the DTC
* The ignition is ON.
* Battery voltage is 9-18 V.
* The fan speed is commanded 6 % or higher.
Conditions for Setting the DTC
* The fan is ON and the current is greater than 8.5 A.
* The fan is ON and the PWM signal current is greater than 3.97 A.
* The fan is ON and the fan tach signal is less than or equal to 24 Hz
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.
Reference Information
Schematic Reference
Hybrid Cooling Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Drive Motor Generator Battery Cooling Description (Drive Motor Generator Battery Cooling Description)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Special Tools
EL-48900 HEV Safety Kit
Circuit/System Verification
1. Ignition ON, observe the scan tool drive motor generator battery temperature parameters. The readings should be between -39 and +69°C (-40 and +156°F).
2. Command the drive motor generator battery coolant fan ON and OFF. You should hear the fan turn ON and OFF, when changing between the commanded states. There is approximately a 5 second delay when the fan is commanded ON.
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.
1. Verify that DTC P0A1F is not set.
• If DTC P0A1F is set, refer to DTC P0A1F, P1A01, P1A05, or P1A06 (P0A1F).
2. Inspect the inlet air vents for any obstructions or blockages that are external to the drive motor generator battery.
• If inlet air obstructions or blockages are found, remove or repair as needed, Clear the DTC and verify the fan operation.
3. Inspect the vent fan for any damage to the fan blades.
• If fan or blades are damaged, replace the drive motor generator battery assembly.
4. Ignition OFF, disable the high voltage at the drive motor generator battery. Refer to High Voltage Disabling (High Voltage Disabling).
5. Ignition OFF, Remove the drive motor battery coolant cover. Refer to Drive Motor Battery Coolant Cooler Cover Replacement (Drive Motor Battery Coolant Cooler Cover Replacement).
6. Disconnect the X 456 inline harness connector at the side of the drive motor generator battery assembly.
7. Test for less than 5 Ohms between the ground circuit terminal E and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance. If the circuits test normal, replace the drive motor generator battery control module.
8. Connect a test lamp between the control circuit terminal A and ground circuit terminal F.
9. Ignition OFF, connect the 12 V battery.
10. Ignition ON, command the drive motor battery coolant fan ON/OFF with a scan tool. The fan should turn ON/OFF when changing between the commanded states.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the drive motor generator battery control module.
11. If all circuits test normal, test or replace the drive motor battery coolant fan.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Drive Motor Battery Coolant Cooler Replacement (Drive Motor Battery Coolant Cooler Replacement)
* Drive Motor Battery Sensor Module Wiring Harness Replacement (Drive Motor Battery Sensor Module Wiring Harness Replacement)
* Drive Motor Generator Battery Replacement (Drive Motor Generator Battery Control Module and Bracket Replacement)
* Control Module References (Programming and Relearning) for drive motor generator battery control module replacement, setup and programming.