P2797

DTC P2797 (Hybrid)

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 P2797
- Auxiliary Transmission Fluid Pump Performance

Circuit/System Description

The auxiliary transmission fluid pump is an electrical device that is used with the auxiliary transmission fluid pump relay to maintain transmission fluid line pressure to the transmission during Engine Idle Off mode. The ECM monitors the transmission fluid pressure switch (TFP) to verify that the auxiliary transmission pump is maintaining the proper amount of pressure. The auxiliary transmission fluid pump attaches to the transmission side cover assembly. The auxiliary transmission fluid pump relay receives voltage through the battery positive voltage circuit. The starter generator control module (SGCM) controls the auxiliary pump by providing the ground path on the auxiliary pump relay control circuit sending power to the hybrid pump driver (HPD). The SGCM monitors all of the circuits of the auxiliary transmission fluid pump control circuits.

Conditions for Running the DTC

* The engine is not running and is in Hybrid engine OFF mode.
* The auxiliary transmission fluid pump is commanded ON.

Conditions for Setting the DTC

The auxiliary transmission fluid pump is commanded ON and the transmission fluid pressure (TFP) switches remain open for 30 seconds or more.

Action Taken When the DTC Sets

* DTC P2797 is a Type B DTC.
* The SGCM inhibits auxiliary transmission fluid pump operation.
* The SGCM inhibits Engine Idle Off mode.

Conditions for Clearing the DTC

DTC P2797 is a Type B DTC.

Reference Information
Description and Operation

Starter/Generator Description and Operation ()
DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

J 21867 Pressure Gage

Circuit/System Verification

1. If DTC P0B09, P1808, P1809 or P2796 is set diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions).
2. Perform the Transmission Fluid Check (Transmission Fluid Checking Procedure) to verify correct fluid level and condition. The transmission fluid level should be within the crosshatch band and the transmission fluid should be red or dark brown.

• If the transmission fluid is low or discolored, refer to Transmission Fluid Check (Transmission Fluid Checking Procedure).

3. Ignition ON, engine OFF, command the ECM Aux Trans Pump ON and OFF with a scan tool. Listen for the auxiliary transmission pump operation. A stethoscope may be necessary to hear pump operation.
4. 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 observe from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition ON, engine OFF, observe the scan tool ECM TFP switch A parameter should read Low. Engine running, observe the scan tool ECM TFP switch A parameter should read High

• If not the specified value, test or replace the TFP manual valve position switch.

2. Ignition OFF, Install J 21867 at the line pressure tap.
3. Ignition ON, engine OFF. Command the ECM Aux Trans Pump ON with the scan tool. The Pressure should be greater than 20 PSI.

• If less than the specified value, inspect for:

* Restricted transmission fluid pump pickup filter
* Kinked or pinched auxiliary fluid pump inlet/outlet pipes, and transmission cooler lines.

• If no problems are found, replace the auxiliary transmission fluid pump.

4. Test or replace the Auxiliary transmission fluid pump check valve.

Repair Instructions

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

* Transmission Fluid Check (Transmission Fluid Checking Procedure)
* Auxiliary Fluid Pump Replacement (Auxiliary Fluid Pump Replacement)
* Transmission Fluid Pressure Manual Valve Position Switch Replacement (Service and Repair)
* Auxiliary Fluid Pump Outlet Pipe Replacement (Auxiliary Fluid Pump Outlet Pipe Replacement)
* Auxiliary Fluid Pump Removal (L4 Hybrid Only) (Overhaul) for check valve replacement