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DTC P079B

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 P079B: Transmission Clutch 2 Slip Detected

Typical Scan Tool Data

Variable Hi and 2-3-4 Clutch Reference

Parameter

Commanded ON

Commanded OFF

Slipping when Commanded ON

Operating Conditions: Vehicle speed 0-80 km/h (0-50 mph)

Parameter Normal Range: 0-6,000 RPM

Clutch 2 Slip Speed

0 RPM

0-6,000 RPM

0-6,000 RPM

Clutch 2 Status

Applied

Released

Applied

Circuit/System Description

The transmission control module (TCM) monitors Clutch 2 Slip Speed for each Hybrid Transmission Mode Commanded state. The transmission control module monitors clutch slip when the variable high, 2-3-4 clutch is commanded ON.

Conditions for Running the DTC
    • Variable hi and 2-3-4 clutch is applied.
    • The clutch pressure control solenoid valve 2 commanded pressure is 1800 kPa (261 psi) for 3 seconds.

Conditions for Setting the DTC
    • The TCM detects the variable hi and 2-3-4 clutch slip is greater than 200 RPM for greater than 1 second 3 times within the same key cycle. The TCM retries at 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
    • P079B is a Type A DTC.
    • The TCM inhibits Single Electric Motor and Duel Electric Motors and ICE mode.

Conditions for Clearing the DTC

P079B 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

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

    •  Transmission General Description
    •  Electronic Component Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Verify that DTCs P0721, P0723, P0776, P0777, 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 Dual Motors mode. The Clutch 2 Slip Speed parameter reading should be less than 200 RPM when the Clutch 2 Status parameter reading is Applied.

Component Testing
  1. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection to verify Q8 control solenoid valve assembly condition.
  2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test to verify Q8 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 variable hi and 2-3-4 clutch and drive motor/generator stator cooling regulator boost valve for sticking or damage.
    5. ⇒If you found cause for concern in the variable hi and 2-3-4 clutch and drive motor/generator stator cooling regulator boost valve, repair or replace the valve or valve body.
  5. Inspect the variable hi and 2-3-4 clutch assembly piston, snap ring, and clutch discs for a damaged condition.
    6. ⇒If you found the variable hi, 2-3-4 clutch to be damaged, repair or replace the variable high, 2-3-4 clutch as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    • Variable High and 2-3-4 Clutch Hub and Clutch Removal and Variable High and 2-3-4 Clutch and Hub Installation for variable High, 2-3-4 Clutch replacement
    • Control Valve Body Replacement for control valve body replacement.
    •  Control Valve Body Diagnostic Inspection
    • Transmission Replacement for Transmission removal
    •  Control Module References for Control Solenoid Valve Assembly and Transmission Control Module Assembly replacement, programming, and setup.
   


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