GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2008 🢒 Astra 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 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 P0121 or P1125.
    • No Transmission Range (TR) Switch DTC P0705.
    • No Transmission Fluid Temperature (TFT) Sensor DTCs P0711, P0712, or P0713.
    • No Speed Sensor DTCs P0717 or P0722.
    • No Pressure Control (PC) Solenoid DTCs P0961-P0963 or P0965-P0967.
    • No Shift Solenoid (SS) Control Circuit DTCs P0973, P0974, P0976, P0977, P0979, P0980.
    • No Transmission Torque Delivered Circuit DTC P2637.
    • Throttle position is greater than 10 percent.
    • Engine speed is greater than 2000 RPM.
    • Input Speed is between 150-6000 RPM.
    • Range equals D for greater than 8 seconds.
    • Transmission oil temperature is greater than 20°C (68°F).
    • Engine torque is greater than 50 N·m (37 lb ft).
    • Current gear is greater than 1st.
    • Not in Emergency Mode.

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
    • DTC 742 is a Type C DTC.
    • No L-up control.
    • No neutral control.
    • The transmission will operate in 1st gear when vehicle speed is less than 10 km/h (6 mph).

Conditions for Clearing the DTC

DTC P0742 is a Type C DTC.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Information

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. Operate the vehicle in 2nd gear. The engine should not stall when shifting into 2nd gear.
  2. Firmly apply the parking brake, select D, drive, using the Shift Control. Observe the scan tool Torque Converter Slip parameter with the brake pedal released. The parameter should be greater than 90 percent.
  3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Ignition ON, observe the DTC information with a scan tool.

Circuit/System Testing
  1. Perform a line pressure test. Refer to Line Pressure Check procedure.
  2. Remove the control valve body cover. Refer to Control Valve Body Cover Removal procedure.
  3. Inspect the inside of the control valve body cover for excessive sediment. There should not be excessive sediment.
    4. ⇒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 Clutch Assembly Assemble , and Transmission Fluid Pump Cleaning and Inspection procedures.
    ⇒If all conditions test normal, test or replace the transmission.
  4. Verify that the control valve body has been serviced within the past 3 months.
    5. ⇒If the control valve body has not been serviced, replace the control valve body assembly. Refer to Control Valve Body Assembly Installation , Control Valve Body Assembly Removal procedures.
  5. If all circuits and components test normal, replace the transmission.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Line Pressure Check
    •  Control Valve Body Cover Removal
    •  Torque Converter Assembly Removal
    •  Forward Clutch Assembly Assemble
    •  Transmission Fluid Pump Cleaning and Inspection
    •  Control Valve Body Assembly Installation
    •  Control Valve Body Assembly Removal