P2797
DTC P2797
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 Descriptor
DTC P2797
- Auxiliary Transmission Fluid Pump Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The auxiliary transmission fluid pump system supplies the transmission with hydraulic pressure when the vehicle is operating in the internal combustion engine Autostop hybrid mode. The auxiliary transmission fluid pump system consists of an auxiliary transmission fluid pump control module that operates an electric, 12V 3 phase alternating current (ac), motor-driven pump. Two pulse width modulated (PWM) status circuits connect the auxiliary transmission fluid pump control module to the hybrid powertrain control module. The transmission auxiliary oil pump control circuit delivers the hybrid powertrain control module commanded pump speed to the auxiliary transmission fluid pump control module. The transmission auxiliary oil pump diagnostic circuit supplies the hybrid powertrain control module with the actual pump speed and also with the operating status of the auxiliary transmission fluid pump control module. The hybrid powertrain control module monitors these circuits for fault conditions.
The auxiliary transmission fluid pump control module inverts 12V direct current (dc) into 12V, 3 phase ac current to operate the pump motor.
The auxiliary transmission fluid pump control module monitors the status of the auxiliary transmission fluid pump motor/pump as well as its own internal circuitry. The auxiliary transmission fluid pump control module does not store its own diagnostic status. Current ignition cycle diagnostic status is reported to the hybrid powertrain control module over the transmission auxiliary oil pump diagnostic circuit. The diagnostic status within the auxiliary transmission fluid pump control module is reset at every ignition-off cycle.
Conditions for Running the DTC
* Ignition voltage is 8-18 volts.
* The auxiliary transmission fluid pump is commanded ON.
Conditions for Setting the DTC
The hybrid powertrain control module observes the difference between actual and commanded auxiliary transmission fluid pump pump speed is greater than 500 RPM for 4 out of 4.125 seconds.
Action Taken When the DTC Sets
* DTC P2797 is a Type B DTC.
* The drive motor generator power inverter control module disables the Autostop hybrid mode.
Conditions for Clearing the DTC
DTC P2797 is a Type B DTC.
Reference Information
Schematic Reference
Hybrid Controls Schematics (Hybrid Controls Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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
J 38522 - Variable Signal Generator
For equivalent regional tools, refer to Special Tools (Hybrid Controls).
Circuit/System Verification
1. Ignition ON with the engine OFF, command the Aux. Trans. Pump Speed to 50 percent with the scan tool. Attempt to maintain pump operation for at lease 60 seconds.
2. Observe the aux. trans. fluid pump actual display and the aux. trans. fluid pump commanded displays with the scan tool. Actual pump speed should be maintained within 10 percent of commanded. The pump should not make excessive noise or stall.
• If the actual speed is within 10 percent of commanded speed an electrical fault condition is not currently present, if an aux. trans. fluid pump pressure fault is suspected, test the aux. trans. pump line pressure output. Refer to Line Pressure Check (Line Pressure Check).
• If the difference between actual and commanded speed is greater than 10 percent, the pump is noisy, or the pump stalls, proceed to Circuit/System Testing.
Circuit/System Testing
1. Inspect for DTC P0C2B. Diagnose P0C2B before performing this procedure.
2. Ignition ON, engine OFF, observe the Aux. Trans. Fluid Pump Fault Status 1 and Aux. Trans. Fluid Fault Status 2 displays with the scan tool.
3. Command the aux. trans. fluid pump speed to 50 percent with the scan tool while observing the fault status displays.
• Refer to the applicable diagnostic procedure below for the fault status indicated by the scan tool display.
• If No Fault status is displayed, review the Freeze Frame/Failure Records and perform the diagnosis indicated by the Fault Status parameter display.
PWM Input Fault
1. Ignition OFF, disconnect power inverter module connector X1.
2. Ignition ON, test for 11-13V on the Trans. Aux. Oil Pump Control circuit from power inverter module connector X1 terminal 3 and chassis ground.
• If less than the specified range, test the control circuit for an open or short to ground. If the circuit tests normal, replace the auxiliary transmission fluid pump Control Module.
Note: Only connect the J 38522 - variable signal generator to the auxiliary transmission fluid pump control circuit when adjusted to 50 percent duty cycle. Duty cycles of less than 50 percent may damage the auxiliary transmission fluid pump assembly.
3. Pre-Adjust the J 38522 - variable signal generator to 50 percent duty cycle @ 250 Hz.
4. Connect the J 38522 - variable signal generator to the Trans. Aux. Oil Pump Control circuit, from the power inverter module connector X1 terminal 3 and ground and listen for auxiliary transmission fluid pump motor operation.
• If pump operation is audible, replace the power inverter module.
• If pump operation is not audible, continue with Circuit/System Testing.
5. Ignition OFF, disconnect the auxiliary transmission fluid pump control module connector X1.
6. Ignition ON, test for 0V on the Trans. Aux. Oil Pump control circuit from power inverter module connector X1 terminal 3 and chassis ground.
• If greater than the specified range, test the control circuit for a short to voltage.
• If equal to the specified range, replace the auxiliary transmission fluid pump control module.
Motor/Open Short
This display indicates the auxiliary transmission fluid pump control module has detected one of the following pump motor current conditions:
* At least one phase current is more than 70 A.
* Commanded current is more than 5 A and actual current in any phase is less than 2 A.
1. Ignition OFF, disconnect the auxiliary transmission fluid pump control module connector X2.
2. Using the Auxiliary Fluid Pump Specification table listed below, test the resistance between the X2 circuits of the pump connector as indicated.
• If any of the circuits are not within the specified range, replace the pump assembly and repeat the Circuit/System Verification.
• If all circuits test normal, replace the auxiliary transmission fluid pump control module and repeat Circuit/System Verification.
Motor CKT Fault
This display indicates an internal auxiliary transmission fluid pump control module fault exists, no external circuits are involved. Replace the auxiliary transmission fluid pump control module.
Temp Sen Fault
This display indicates an internal auxiliary transmission fluid pump control module fault exists, no external circuits are involved. Replace the auxiliary transmission fluid pump control module.
Low Voltage
1. This display indicates the auxiliary transmission fluid pump control module has monitored battery voltage of less than 12.6V.
2. Measure actual battery voltage with a DMM.
• If actual battery voltage measures less than the value range, increase actual battery voltage and repeat Circuit/System Testing.
• If actual battery voltage measures more than the value range, test the auxiliary transmission fluid pump control module power and ground circuits for a high resistance condition. If the circuits test normal, replace the auxiliary transmission fluid pump control module.
Auxiliary Transmission Fluid Pump Control Module Over temp
1. This display indicates the auxiliary transmission fluid pump control module circuit board has reached a temperature of 115-125°C (239-257°F).
2. Measure the actual temperature of the auxiliary transmission fluid pump control module case.
• If actual temperature is the same or more than the value range, no action is necessary.
• If actual temperature is less than the value range, replace the auxiliary transmission fluid pump control module.
Auxiliary Transmission Fluid Pump Control Module Hot
1. This display indicates the auxiliary transmission fluid pump control module circuit board has reached a temperature of more than 125°C (257°F).
2. Measure the actual temperature of the auxiliary transmission fluid pump control module case.
• If actual temperature is the same or more than the value range, no action is necessary.
• If actual temperature is less than the value range, replace the auxiliary transmission fluid pump control module.
Current High/Lo
1. This display indicates the auxiliary transmission fluid pump control module has monitored motor current that is outside the normal range for a given motor speed.
2. Inspect for the following conditions:
* Low or cavitating automatic transmission fluid
* Poor terminal connection or wiring degradation
* External indication of auxiliary transmission fluid pump pump motor damage
• If none of the conditions are observed, replace the auxiliary transmission fluid pump motor/pump assembly and the auxiliary transmission fluid pump control module.
Current Fault
This display indicates an internal auxiliary transmission fluid pump control module fault exists, no external circuits are involved. Replace the auxiliary transmission fluid pump control module.
Unable to Start
1. This display indicates the auxiliary transmission fluid pump control module has monitored motor current of more than 20 A during motor start-up.
2. Inspect for the following conditions:
* Automatic transmission fluid pressure trapped internally
* Poor terminal connection or wiring degradation
* External indication of auxiliary transmission fluid pump pump motor damage
• If none of the conditions are observed, replace the auxiliary transmission fluid pump motor/pump assembly and the auxiliary transmission fluid pump control module.
No PWM Response
This display indicates the hybrid powertrain control module does not detect the auxiliary transmission fluid pump Control Feedback circuit signal. Refer to DTC P0C2B (P0C2B).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Control Module References (Control Module References) for power inverter module or auxiliary transmission fluid pump control module replacement, setup, and programming
* Auxiliary Fluid Pump and Gasket Replacement (Auxiliary Fluid Pump and Gasket Replacement)