DTC P2797 Hybrid

Diagnostic Instructions

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

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

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

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 21867 Pressure Gage

Circuit/System Verification

1. Verify that DTC P0B09, P1808, P1809 or P2796 is not set.

⇒	If any of the DTCs are set, refer to Diagnostic System Check - Vehicle.

2. Perform the Transmission Fluid Check 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.

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.

Circuit/System Testing

1. Ignition OFF, Install J 21867 at the line pressure tap.
2. 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 auxiliary transmission fluid pump pickup filter

•	Restricted auxiliary transmission fluid pump pickup filter

•	Kinked or pinched auxiliary fluid pump inlet/outlet pipes

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

3. Test or replace the TFP manual valve position switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Diagnostic Instructions

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

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

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

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 21867 Pressure Gage

Circuit/System Verification

1. Verify that DTC P0B09, P1808, P1809 or P2796 is not set.

⇒	If any of the DTCs are set, refer to Diagnostic System Check - Vehicle.

2. Perform the Transmission Fluid Check 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.

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.

Circuit/System Testing

1. Ignition OFF, Install J 21867 at the line pressure tap.
2. 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 auxiliary transmission fluid pump pickup filter

•	Restricted auxiliary transmission fluid pump pickup filter

•	Kinked or pinched auxiliary fluid pump inlet/outlet pipes

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

3. Test or replace the TFP manual valve position switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.