P079C

DTC P079C

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 P079C
- Transmission Clutch 3 Slip Detected

Circuit/System Description

The transmission control module monitors the 4th clutch slip Speed when the 4th clutch is applied. The 4th clutch is displayed as Clutch 3 on the scan tool. The transmission control module is part of the control solenoid valve assembly and is not serviced separately.

Conditions for Running the DTC

The clutch PC solenoid 3 commanded pressure is 1800 kPa (261 psi).

Conditions for Setting the DTC

The transmission control module detects the 4th clutch slip speed is greater than 100 RPM for greater than 1 second.

Action Taken When the DTC Sets

* P079C is a Type B DTC.
* The transmission control module 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
DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)

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 is not set.

• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).

2. Perform the Transmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) to verify correct fluid level.
3. Perform the Line Pressure Check (Line Pressure Check) to verify correct oil pressure.
4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection) to verify Q8 control solenoid valve assembly condition.
5. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test) to verify Q8 control solenoid valve assembly function.
6. 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.

7. 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.

8. 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.

* Control Valve Assembly Disassemble ()for Valve Body Inspection procedures.
* Control Valve Upper Body Replacement (2ML70 - Automatic Transmission)for Control Valve Body replacement.
* 4th Clutch Piston Removal ()for 4th Clutch inspection.
* 4th Clutch Piston Installation ()for 4th Clutch Assembly replacement.
* Control Module References (Control Module References)for Control Solenoid Valve Assembly replacement, programming and setup.