P079C
DTC P079C
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (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 P079C
- Transmission Friction Element 3 Slip Detected
Typical Scan Tool Data
Circuit/System Description
The transmission control module (TCM) monitors the Clutch Slip Speed for each Hybrid Trans. Mode Commanded state. Clutch 3 is commanded ON in 4th gear. This DTC detects excessive clutch slip speed when clutch 3 is commanded ON, indicating a slipping clutch condition.
Conditions for Running the DTC
The clutch PC solenoid 3 commanded pressure is 1800 kpa (261 psi) for 3 seconds.
Conditions for Setting the DTC
The TCM detects the clutch 3 slip speed is greater than 100 RPM for greater than 3 seconds.
Action Taken When the DTC Sets
* P079C is a Type B DTC.
* The TCM inhibits gear 4.
Conditions for Clearing the DTC
P079C 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. Operate the vehicle from 3rd through 4th gear while observing the Clutch 3 Slip Speed parameter. Stop the vehicle and turn the ignition OFF for 30 seconds. Perform this action 2 times. The Clutch 3 Slip Speed parameter should display near 0 RPM when the Clutch 3 Status parameter displays Applied.
• If any other transmission DTCs are set, diagnose those first.
• If DTC P079C 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 TCM 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 hybrid low, 1-2 clutch boost valve assembly and the hybrid low, 1-2 clutch regulator valve assembly for sticking or damage.
• If you found a concern with the hybrid low, 1-2 clutch boost valve assembly or the hybrid low, 1-2 clutch regulator valve assembly, repair or replace the valve or valve body.
5. Inspect the 4th clutch assembly for a slipping or damaged condition.
• If you found a 4th clutch assembly concern, repair or replace the low and reverse clutch assembly as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* 4th Clutch Piston Removal (Overhaul) and 4th Clutch Piston Installation (Overhaul) for 4th clutch assembly replacement.
* Control Solenoid Valve and Transmission Control Module Assembly Replacement (Control Solenoid Valve and Transmission Control Module Assembly Replacement) for lower valve body assembly repair or replace.
* Perform the valve body inspection procedure, refer to Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and TCM Assembly Solenoid Performance Test). If the inspection procedure indicates to replace the valve body, refer toControl Solenoid Valve and Transmission Control Module Assembly Replacement (Control Solenoid Valve and Transmission Control Module Assembly Replacement) and Control Valve Upper Body Replacement (Service and Repair).
* Control Module References (Programming and Relearning) for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming.