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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 Clutch 1 Slip Detected

Typical Scan Tool Data

Variable Low and 1-2 Reverse Clutch Reference

Parameter

Commanded ON

Commanded OFF

Slipping when Commanded ON

Operating Conditions: Vehicle speed 0-161 km/h (0-100 mph)

Parameter Normal Range: 0-6,000 RPM

Clutch 1 Slip Speed

0 RPM

0-6,000 RPM

0-6,000 RPM

Clutch 1 Status

Applied

Released

Applied

Circuit/System Description

The transmission control module (TCM) monitors the Clutch 1 Slip Speed for each Hybrid Transmission Mode Commanded state. The transmission control module monitors clutch slip when the variable Low and 1-2 reverse clutch is applied. The transmission control module is part of the control solenoid valve assembly and is not serviced separately.

Conditions for Running the DTC
    • The clutch pressure control solenoid valve 3 commanded pressure is 1800 kPa (261 psi) for 3 seconds.
    • The variable low and 1-2 reverse clutch torque estimated is greater than 200 N·m (148 lb ft).
    • The variable low and 1-2 reverse clutch fill detected.
    • The commanded mode is:
       - Reverse
       - Dual Electric Motors
       - Dual Electric Motors and ICE

Conditions for Setting the DTC
    • The transmission control module detects Hybrid low, 1-2 clutch slip greater than 200 RPM for 3 seconds.
    • C1 slip greater than 200 RPM for greater than 1 second 3 times during one key cycle. Retries are 30 seconds apart.
    • Motor 1 or 2 are approaching over-speed limits due to clutch slip, the fault will set instantly.

Action Taken When the DTC Sets
    • P079A is a Type A DTC.
    • The transmission control module inhibits:
       - Dual Electric Motors
       - Dual Electric Motors and ICE

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. 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

Description and Operation

    •  Transmission General Description
    •  Transmission Component and System Description
    •  Electronic Component Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Verification
  1. Verify that DTCs P0721, P0796, P0966, P0967, P0969, P0970, P0971, P0973, P0974, P0976, P0977, P215C, P2720, P2721, P2728, P2729, or P2730 is not set.
    2. ⇒ If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Perform the Transmission Fluid Level and Condition Check to verify correct fluid level and condition.
  3. Perform the Line Pressure Check to verify correct oil pressure.
  4. Operate the vehicle in Duel Electric Motors and Duel Electric Motors and ICE mode. The Clutch 1 Slip Speed parameter reading should be less than 200 RPM when the Clutch 1 Status parameter reading is Applied.

Component Testing
  1. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection to verify control solenoid valve assembly condition.
  2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test to verify control solenoid valve assembly function.
    3. ⇒If a malfunction is found, replace the Q8 control solenoid valve assembly.
  3. Inspect the a/trans fluid level control valve for stuck closed or damaged condition.
    4. ⇒If you found cause for concern in the a/trans fluid level control valve, replace the a/trans fluid level control valve.
  4. Inspect the valve body components and hydraulic circuits listed below for a leak or a stuck valve:
    5. • Control valve body spacer (w/gasket) plate assembly
    • 1-3 reverse clutch and drive motor/generator stator cooling regulator valve
    ⇒If you found cause for concern in the valve body, repair or replace the valve or valve body.
  5. Inspect the 1-3 reverse clutch assembly snap ring, piston, clutch discs, and housing for a slipping or damaged condition.
    6. ⇒If you found cause for concern in the 1-3 reverse clutch assembly, repair or replace the 1-3 reverse assembly as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    • Control Valve Body Assembly Disassemble for Valve Body inspection procedures.
    • Control Valve Body Replacement for control valve body replacement.
    • Variable Low and 1-2 Reverse Clutch Piston Removal and Variable Low and 1-2 Reverse Clutch Piston Installation for 1-3-Reverse Clutch Assembly replacement.
    •  Control Module References for Control Solenoid Valve Assembly and Transmission Control Module Assembly replacement, programming, and setup.

   


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