P2797
DTC P2797
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* 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 (ATFP) system supplies the transmission with hydraulic pressure when the vehicle is operating in the internal combustion engine (ICE) Autostop hybrid mode. The ATFP system consists of a ATFP control module that operates an electric 3 phase alternating current (ac), motor-driven pump. Two PWM status circuits connect the ATFP control module to the hybrid powertrain control module (HPCM). The transmission auxiliary oil pump control circuit delivers the HPCM commanded pump speed to the ATFP control module. The transmission auxiliary oil pump diagnostic circuit supplies the HPCM with the actual pump speed and also with the operating status of the ATFP control module. The HPCM monitors these circuits for fault conditions.
The ATFP control module inverts 12 v direct current (dc) into 12 v, 3 phase ac current to operate the pump motor.
The ATFP control module monitors the status of the ATFP pump as well as it's own internal circuitry. The ATFP control module does not store it's own diagnostic status. Current ignition cycle diagnostic status is reported to the HPCM on the transmission auxiliary oil pump diagnostic circuit. The diagnostic status within the ATFP 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 HPCM observes the difference between actual and commanded ATFP pump speed is more than 500 RPM for 2.5 out of 3 seconds.
Action Taken When the DTC Sets
* DTC P2797 is a Type B DTC.
* The PIM disables the Autostop hybrid mode.
Conditions for Clearing the DTC
DTC P2797 is a Type B DTC.
Special Tools Required
J 38522 Variable Speed Generator
Circuit/System Verification
1. Ignition ON with the engine OFF, command the aux. trans. fluid pump speed to 50 % with the scan tool.
2. Observe the aux. trans. fluid pump actual display. Actual pump speed should be within 10% of commanded.
^ If the actual speed is within 10% of commanded speed an electrical fault condition is not present, test the aux. trans. pump line pressure output.
^ If the actual speed is more than 10% different than commanded speed, 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 % with the scan tool.
^ Refer to the applicable diagnostic procedure below for the fault status indicated by the scan tool display.
^ If no fault status is displayed, test the aux. trans. pump line pressure output.
PWM Input Fault
1. Ignition OFF, disconnect drive motor generator power inverter control module (PIM) connector X1.
2. Ignition ON, test for 11-13 V on the Trans. Aux. Oil Pump Control circuit from PIM connector X1 terminal 5 and chassis ground.
^ If less than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ATFP Control Module.
Important: Only connect the J 38522 to the ATFP control circuit when adjusted to 50% duty cycle. Duty cycles of less than 50% may damage the ATFP pump assembly.
3. Pre-Adjust the J 38522 variable signal generator to 50% duty cycle @ 250 Hz.
4. Connect the J 38522 variable signal generator to the Trans. Aux. Oil Pump Control circuit, from the PIM connector X1 terminal 5 and ground and listen for ATFP motor operation.
^ If pump operation is audible, replace the PIM.
^ If pump operation is not audible, replace the ATFP control module.
Motor / Open Short
1. This display indicates the ATFP 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.
2. Ignition OFF, disconnect ATFP connector X1.
3. Measure the resistance of the phase circuits as indicated below. You should measure 4kohm - 8kohm.
* X1 terminal A to C
* X1 terminal A to E
* X1 terminal C to E
^ If not within the value range, replace the ATFP motor assembly.
4. Measure the resistance of the phase circuits as indicated below. You should measure infinite resistance.
* X1 terminal A to ground
* X1 terminal C to ground
* X1 terminal E to ground
^ If not within the value range, replace the ATFP motor assembly.
5. If all circuits test normal, replace the ATFP control module.
Motor Power Drive Circuit
This display indicates an internal ATFP control module fault exists, no external circuits are involved. Replace the ATFP control module.
Temperature Sensor Open/Short
This display indicates an internal ATFP control module fault exists, no external circuits are involved. Replace the ATFP control module.
Low Voltage
1. This display indicates the ATFP control module has monitored battery voltage of less than 12V (±5%).
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 ATFP control module power and ground circuits for a high resistance condition. If the circuits test normal, replace the ATFP control module.
MOSFET Overtemperature
1. This display indicates the ATFP control module circuit board has reached a temperature of 115°C - 125°C (239°F - 257°F).
2. Measure the actual temperature of the ATFP 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 ATFP control module.
MOSFET Hot
1. This display indicates the ATFP control module circuit board has reached a temperature of more than 125°C (257°F).
2. Measure the actual temperature of the ATFP 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 ATFP control module.
Motor Current Out of Range
1. This display indicates the ATFP 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 ATFP pump motor damage
^ If none of the conditions are observed, replace the ATFP motor assembly and the ATFP control module.
Processor Fault
This display indicates an internal ATFP control module fault exists, no external circuits are involved. Replace the ATFP control module.
Unable to Start
1. This display indicates the ATFP control module has monitored motor current of more than 20 A during motor start-up.
2. Inspect for the following conditions:
* Trapped automatic transmission fluid pressure
* Poor terminal connection or wiring degradation
* External indication of ATFP pump motor damage
^ If none of the conditions are observed, replace the ATFP motor assembly and the ATFP control module.
PWM Failure
This display indicates the PIM does not detect the ATFP Control Feedback circuit signal. Refer to DTC P0C2B. P0C2B
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Programming and RelearningProgramming and Relearning
* Auxiliary transmission fluid pump assembly. Refer to Automatic Transmission Auxiliary Fluid Pump and Gasket Replacement.