P079A

DTC P079A

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 P079A
- Transmission Clutch 1 Slip Detected

Circuit/System Description

The transmission control module monitors the hybrid low, 1-2 clutch slip speed when the hybrid low, 1-2 clutch is applied. The hybrid low, 1-2 clutch is displayed as Clutch 1 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).
* The commanded gear is:

- Reverse
- Mode 1
- Gear 1
- Gear 2

Conditions for Setting the DTC

The transmission control module detects Hybrid low, 1-2 clutch slip greater than 200 RPM for 3 seconds.

Action Taken When the DTC Sets

* P079A is a Type A DTC.
* The transmission control module inhibits Reverse, Mode 1, Gear 1 and Gear 2.

Conditions for Clearing the DTC

P079A is a Type A DTC.

Diagnostic Aids

When attempting to set transmission performance DTCs, observe the Freeze Frame and Failure Records to assist in duplicating the failure conditions. An auxiliary transmission fluid pump producing low output pressure may cause a clutch slip condition. The Aux. Trans. Fluid Pump Actual parameter should be within 25 percent of the Aux. Trans. Fluid Pump Commanded parameter. 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, P0756, P0757, P0796, P0797, P0966, P0967, P0969, P0970, P0971, P0973, P0974, P0976, P0977, P2720, P2721, P2728, P2729, P2730, P2797, or P0C2B 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 and condition.
3. Verify using Freeze Frame and Failure Records, the Aux. Trans. Fluid Pump Actual parameter is within 25 percent of the Aux. Trans. Fluid Pump Commanded parameter.

• If the Aux. Trans. Fluid Pump Actual parameter is not within 25 percent of the Aux. Trans. Fluid Pump Commanded parameter, refer to Auxiliary Fluid Pump Pressure High or Low (Auxiliary Fluid Pump Pressure High or Low).

4. Perform the Line Pressure Check (Line Pressure Check) to verify correct oil pressure.
5. 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.
6. 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.
7. Inspect the trans fluid pump ball check valve for possible sticking or damage.

• If you found a concern with the check ball, repair the concern.

8. Inspect the hybrid low, 1-2 clutch regulator valve for sticking or damage.

• If you found a concern with the hybrid low, 1-2 clutch regulator valve, repair or replace the valve or valve body.

9. Inspect the hybrid low, 1-2 clutch assembly for wear or damage.

• If you found a hybrid low, 1-2 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.
* Hybrid Low, 1-2 Clutch Piston Removal ()for Hybrid Low, 1-2 Clutch Assembly inspection.
* Hybrid Low, 1-2 Clutch Piston Installation ()for Low and Hybrid Low, 1-2 Clutch Assembly replacement.
* Control Module References (Control Module References) for Control Solenoid Valve Assembly replacement, programming and setup.