P079D
DTC P079D
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 P079D
- Transmission Clutch 4 Slip Detected
Typical Scan Tool Data
Circuit/System Description
The transmission control module (TCM) monitors the Clutch Slip for each Hybrid Trans. Mode Commanded state. This DTC detects clutch slip when the 1-3 reverse clutch is commanded Applied, indicating a slipping clutch condition.
Conditions for Running the DTC
The clutch PC solenoid 4 commanded pressure is 1800 kpa (261 psi) for 300 milliseconds.
Conditions for Setting the DTC
The TCM detects the 1-3 reverse clutch slip is greater than 100 RPM for greater than 300 milliseconds.
Action Taken When the DTC Sets
* P079D is a Type B DTC.
* The TCM inhibits gear 1 and gear 3.
Conditions for Clearing the DTC
P079D is a Type B DTC.
Diagnostic Aids
When attempting to set transmission performance DTCs, observe the Freeze Frame and Failure Records to assist in duplicating the failure conditions. Ensure the transmission fluid level is correct and there are no leaks. If there are any other transmission DTCs set, diagnose those first.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
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)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Circuit/System Verification
1. Verify that DTCs P0721, P0722, P0723, P0966, P0967, P0969, P0970, P0971, P0973, P0974, P0976, P0977, P2720, P2721, P2728, P2729, or P2730 are not set.
• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions).
2. Clear the DTC.
3. Perform the Transmission Fluid Check (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 Replacement (Removal and Replacement).
4. Engine idling at operating temperature. Attempt to clean or free up a potential sticking valve with the scan tool Service Cleaning Procedure. Refer to Control Solenoid Valve and Transmission Control Module Assembly Cleaning (Control Solenoid Valve and Transmission Control Module Assembly Cleaning) for further instructions.
5. Operate the vehicle from EVT 1 through 4th gear while observing the Clutch 4 Slip Speed parameter. Stop the vehicle and turn the ignition OFF for 30 seconds. Perform this action 2 times. The Clutch 4 Slip speed parameter should display 0 RPM when the Clutch 4 Status parameter displays Applied.
• If any other transmission DTCs set, diagnose those first.
• If DTC P079D resets, go to Component Testing.
Component Testing
1. Perform the Line Pressure Check (Line Pressure Check).
2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test).
• If a concern is found, replace the control solenoid (w/body and TCM) valve assembly.
3. Inspect the trans fluid pump ball check valve for possible sticking or damage.
• If you found a concern with this check ball, repair the concern.
4. Inspect the reverse clutch regulator valve for sticking or damage.
• If you found a concern with the reverse clutch regulator valve, repair or replace the valve or valve body.
5. Inspect the 1-3 reverse clutch assembly for a slipping or damaged condition.
• If you found a 1-3 reverse clutch assembly concern, repair or replace the 1-3 clutch assembly as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* 1-3-Reverse Clutch, Input Carrier, Sun Gear, and Shaft Removal (Overhaul) and 1-3-Reverse Clutch Installation (Overhaul) for 1-3 reverse clutch assembly repair or replacement
* Control Valve Lower Body and Upper Body Replacement (2MT70 - Automatic Transmission) for lower valve body assembly repair or replacement
* Perform the valve body inspection procedure, refer to Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection). If the inspection procedure indicates to replace the valve body, refer to Control Valve Lower Body and Upper Body Replacement (2MT70 - Automatic Transmission).
* Control Module References (Programming and Relearning) for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming
* Transmission Replacement (Removal and Replacement) for transmission removal.