GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1997 🢒 Century 🢒 DTC 🢒 DTC P0742 TCC System Stuck On

Object Number: 28119 Size: MF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The Torque Converter Clutch Solenoid Valve (TCC Sol Valve) acts on the hydraulic fluid, controlling TCC apply and release.

When the PCM detects 3 occurrences of TCC slip is -20 to +25 RPM when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type B DTC.

Conditions for Setting the DTC
    • No TP DTCs P0122 or P0123.
    • No VSS DTCs P0502 or P0503.
    • No TCC PWM solenoid electrical DTC P1860.
    • No TCC enable solenoid electrical DTC P0740.
    • Not in fuel shut off.
    • The engine speed is more than 500 RPM for 5 seconds.
    • The PCM has commanded the TCC OFF.
    • The commanded gear is not 1st.
    • The transmission gear indicates 2nd, 3rd or 4th.
    • The throttle angle is between 14-50%.
    • The engine torque is 95-271 N·m (70-200 lb ft).
    • The TCC slip speed is -20 to +25 RPM, 3 occurrences for 5 seconds.
    • The engine speed is 800-4000 RPM.
    • The vehicle speed is 32-112 km/h (20-70 mph).
    • The last gear change occurred more than 3 seconds ago.

Action Taken When the DTC Sets

The PCM illuminates the Malfunction Indicator Lamp (MIL) after two consecutive trips with a failure reported.

Conditions for Clearing the DTC
    • The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
    • A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

Diagnostic Aids
    • Check for PRNDL DTC P0705. DTC P0705 affects transmission operation. This may set DTC P0742 falsely.
    • Inspect the transmission fluid for debris.

Test Description

The number below refers to the step number on the diagnostic table.

  1. A TCC slip speed of -20 to +25 RPM indicates that this DTC is current. Refer to the Diagnostic Aids. Inspect for PRNDL DTC P0705.

DTC P0742 Torque Converter Clutch System Stuck ON

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Install the Scan Tool ®.
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Record the DTC Freeze Frame and Failure Records.

  3. Start and run the vehicle.
  4. Select TCC Slip Speed on the scan tool.
  5. With the transmission in D4, drive the vehicle through the 1-2 upshift.

In second gear is the TCC Slip Speed within the range specified?

-20 to +25 RPM

Go to Step 3

Go to Diagnostic Aids

3

Inspect for the following conditions:

    • The TCC enable solenoid stuck ON because of sediment.
    • The TCC apply valve stuck ON because of sediment.
    • Refer to Control Valve Body Assembly Inspection, Section 7.

Was a condition found and corrected?

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Go to Step 4

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4

In order to verify your repair, perform the following procedure:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • The gear range is D2, D3 or D4.
    • The commanded gear is not 1st.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • Not in fuel shut off.
    • The engine torque is 95-270 N·m (70-200 lb ft).
    • The throttle position is 14-50%.
    • The PCM commands the TCC OFF.
    • The TCC slip speed is 150-2000 RPM for 5 seconds.
    • The engine speed is 800-4000 RPM.
    • The vehicle speed is 32-112 km/h (20-70 mph).
    • The last gear change occurred more than 3 seconds ago.
  4. Select Specific DTC. Enter DTC P0742.

Has the test run and passed?

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System OK

Begin the diagnosis again. Go to Step 1