P079A

DTC P079A

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.



DTC Descriptor
DTC P079A
- Transmission Friction Element 1 Slip Detected




Typical Scan Tool Data






Circuit/System Description

The transmission control module (TCM) monitors the Low 1-2 Clutch Slip for each Hybrid Trans. Mode Commanded state. This DTC detects clutch slip when the hybrid low 1-2 clutch is applied.


Conditions for Running the DTC

* Hybrid low 1-2 clutch is the primary on-coming clutch.
* The commanded gear is:

- Reverse
- EVT Mode 1
- Gear 1
- Gear 2




Conditions for Setting the DTC

The TCM detects Hybrid low 1-2 clutch slip greater than 200 RPM for 10 seconds.


Action Taken When the DTC Sets

DTC P079A is a Type B DTC.


Conditions for Clearing the DTC

DTC P079A 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
Electrical Information Reference

* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs
* High Voltage Disabling
* High Voltage Enabling

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions


Circuit/System Verification

1. Clear the DTC.
2. Operate the vehicle to induce a shift from 1st through 4th gear while observing the Low 1-2 Clutch Slip parameter. Stop the vehicle and turn the ignition OFF for 30 seconds. Perform this action 2 times. The Low 1-2 Clutch Slip parameter should display 0 RPM when the Low 1-2 Clutch Status parameter displays Applied.

• If any other DTCs set, diagnose that DTC first.
• If the DTC P079A resets, go to Component Testing.




Component Testing

1. Perform the Line Pressure Check (Line Pressure Check) .
2. 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.

3. 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.

4. Inspect the hybrid low 1-2 clutch boost valve assembly for sticking or damage.

• If you found a concern with the hybrid direct 2-3-4 clutch regulator valve, repair or replace the valve or valve body.

5. 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 after completing the diagnostic procedure.

* Control solenoid (w/body and TCM) valve assembly replacement. Refer to Control Module References for replacement, setup, and programming.
* hybrid low 1-2 clutch assembly replacement. Refer to Hybrid Low 1-2 Clutch Overhaul .
* Lower valve body assembly. Refer to Control Valve Body Replacement (Control Valve Body Replacement) .
* Perform the valve body inspection procedure, refer to Control Valve Upper Body Assembly Cleaning and Inspection . If the inspection procedure indicates to replace the valve body, refer to Control Valve Body Replacement (Control Valve Body Replacement) .