P0A85

DTC P0A84 or P0A85

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 Descriptors
DTC P0A84
- Hybrid Battery Pack Cooling Fan Control Circuit Low Voltage

DTC P0A85
- Hybrid Battery Pack Cooling Fan Control Circuit High Voltage




Circuit/System Description

The battery energy control module (BECM) monitors the cooling fan to detect if the fan speed is slower or faster than normal. If a failure is detected, the appropriate DTC will set.


Conditions for Running the DTC

The engine is running.


Conditions for Setting the DTC


P0A84
* Fan control feedback is less than 5 percent.
* Fan state is ON.



P0A85
* Fan control feedback is greater than 95 percent.
* Fan state is ON.
* Fan command is less than 80 percent.



Action Taken When the DTC Sets

The hybrid system is not affected.


Conditions for Clearing the DTC

The fan speed control feedback is normal.


Reference Information
Schematic Reference

Hybrid Cooling Schematics ()
Connector End View Reference

Component Connector End Views (Connector Views)
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

J 35616 GM Approved Terminal Test Kit


Circuit/System Verification

Caution: To help avoid personal injury, be careful when working in the vicinity of the generator battery disconnect control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.


1. Verify the DTC is set current, clear the DTC.
2. Ignition ON, using the scan tool special function command the hybrid cooling fan ON and OFF several times.

• If the hybrid battery pack cooling fan operates as commanded and the DTC resets, continue with Circuit/System Testing.


• If the hybrid pack cooling fan does not operate as commanded, replace the hybrid battery pack cooling fan.




Circuit/System Testing

Important: In order to avoid damaging BECM X1 and X2 connector terminals, the proper test probes should be used. The proper test probes are as follows:



* J-35616-65B for female terminals
* J-35616-64B for male terminals


1. Ignition OFF, disconnect the cooling fan harness connector. Refer to Hybrid Battery Service Disconnect/Connect ().
2. Disconnect BECM harness connector X2.
3. Test the fan tach feedback circuit X2 connector terminal 11 to cooling fan harness connector terminal 4 for a short to voltage or a short to ground.
4. If the circuit test normal replace the BECM.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning) for BECM replacement, setup, and programming