P079B
DTC P079B
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 P079B
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Transmission Clutch 2 Slip Detected
Typical Scan Tool Data
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 overspeed limits due to clutch slip, the fault will set instantly.
Action Taken When the DTC Sets
* DTC P079B is a Type B DTC.
* The TCM inhibits duel electric motors and ICE mode.
Conditions for Clearing the DTC
P079B 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 Hybrid/EV Battery Pack X1
Description and Operation
* Transmission General Description Transmission General Description
* Electronic Component Description Electronic Component Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Programming and Relearning 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.
• 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 Testing and Inspection to verify correct fluid level and condition.
3. Perform the Line Pressure Check 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 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 Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test to verify Q8 control solenoid valve assembly function.
• If a concern is found, replace the Q8 control solenoid valve assembly.
3. Inspect the a/trans fluid level control valve for stuck closed or damaged condition.
• If you found a concern with 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.
• If you found a concern with 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.
• If you found a variable hi, 2-3-4 clutch concern, repair or replace the variable high, 2-3-4 clutch as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Variable High and 2-3-4 Clutch Hub and Clutch Removal Variable High and 2-3-4 Clutch Hub and Clutch Removal and Variable High and 2-3-4 Clutch and Hub Installation Variable High and 2-3-4 Clutch and Hub Installation for variable High, 2-3-4 Clutch replacement
* Control Valve Body Replacement Control Valve Body Replacement for control valve body replacement.
* Control Valve Body Diagnostic Inspection Control Valve Body Diagnostic Inspection
* Transmission Replacement Transmission Replacement for Transmission removal
* Control Module References Programming and Relearning for Control Solenoid Valve Assembly and Transmission Control Module Assembly replacement, programming, and setup.
* Perform the Reset Transmission Adapts Programming and Relearning following all transmission related repairs.