GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Terrain 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC P0742

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 P0742: Torque Converter Clutch (TCC) System - Stuck On

Circuit/System Description

The transmission control module (TCM) controls the torque converter clutch (TCC) lock up pressure control solenoid valve. The solenoid directs the hydraulic fluid for TCC apply and release. When the TCC is released, the engine is coupled by fluid to the transmission.

Conditions for Running the DTC
    • No Throttle Position (TP) Sensor DTC P0120
    • No Transmission Range (TR) Switch DTCs P0706, P0707, or P0708
    • No Transmission Fluid Temperature (TFT) Sensor DTCs P0711, P0712, or P0713
    • No Speed Sensor DTCs P0717, P0722, P0727
    • No Pressure Control (PC) Solenoid DTCs P0962, P0963, P0966, P0967, P0970, or P0971
    • No Shift Solenoid (SS) Control Circuit DTCs P0973, P0974, P0976, P0977, P0979, P0980, P0982, P0983, P0985, or P0986
    • No Transmission Torque Delivered Circuit DTC P2637
    • No Communications DTCs U0100 or U2104
    • Engine speed is greater than 400 RPM
    • Input Speed is less than 3000 RPM
    • Range equals D, M, or L for 8 seconds
    • Transmission oil temperature is greater than 20°C
    • Engine torque is 46-240 ohms
    • The ignition voltage is greater than 10.5 volts

Conditions for Setting the DTC

Engine speed minus input speed is less than 50 RPM for 12 seconds when the TCC is commanded off. Low torque converter slip.

Action Taken When the DTC Sets

The transmission will operate in 5th gear in D or M range, 2nd gear in L range.

Conditions for Clearing the DTC

DTC P0742 is a Type A DTC

Diagnostic Aids

Improper transmission fluid level may cause DTC P0742 to set. Refer to the Transmission Fluid Check procedure.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

    •  Electrical Center Identification Views
    •  Component Connector End Views
    •  Splice Pack Connector End Views
    •  Inline Harness Connector End Views

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
    •  Diagnostic Trouble Code (DTC) List - Vehicle

Scan Tool Reference

Control Module References for scan information.

Circuit/System Verification
  1. Ignition ON, observe the DTC information with a scan tool.
  2. Record Freeze Frame and Failure Records.
  3. Clear DTCs.
  4. Operate the vehicle under the conditions observed in the Failure Records.
  5. Observe the DTC information with the scan tool. Verify that the DTC does not set.
  6. Operate the vehicle in D (drive). Using a scan tool, observe the TCC Slip Speed parameter in 3rd, 4th, and 5th gear while the TCC PC Sol. Ref. Current parameter is less than 100 mA. The TCC Slip Speed parameter should be greater than 50 RPM.

Circuit/System Testing
  1. Engine ON, apply the parking brake, select P (park) using the Shift Control.
  2. Observe the scan tool Transmission ISS parameter. The reading should be within 400-800 RPM.
    3. ⇒If the ISS parameter is not within the specified range, test or replace the Transmission Input Speed Sensor (ISS). Refer to the Input Speed Sensor Replacement procedure.
  3. Perform a line pressure test. Refer to Line Pressure Check procedure.
  4. Remove the Control valve body cover. Refer to Control Valve Body Cover Removal procedure.
  5. Inspect the inside of the control valve body cover for excessive sediment. There should not be excessive sediment.
    6. ⇒If excessive sediment is found inspect and replace as necessary the Torque converter assembly, Input shaft, and Fluid pump stator shaft assembly. Refer to Torque Converter Assembly Removal , Forward and Direct Clutch Assembly Assemble and Transmission Fluid Pump Cleaning and Inspection procedures. If all conditions test normal, test or replace the transmission.
  6. Verify that the control valve body has been serviced within the past 3 months.
    7. ⇒If the control valve body has not been serviced, replace the control valve body assembly. Refer to Control Valve Body Replacement procedure. If all circuits and components test normal, replace the transmission.
  7. If all circuits and components test normal, replace the transmission.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.