GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Monte Carlo 🢒 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 (TCC) solenoid valve is an ON/OFF (normally OFF) valve which controls the converter clutch apply and release. The torque converter clutch pulse width modulation (TCC PWM) solenoid valve works with the TCC solenoid valve to control the clutch apply rate (feel). The PCM controls the duty cycle on the TCC PWM solenoid valve to regulate the feed pressure to the converter clutch regulator valve, which in turn, regulates the converter clutch apply pressure.

When the TCC solenoid valve is OFF, TCC fluid is exhausted through the solenoid. The converter clutch apply valve is held by the converter clutch spring and line pressure. In this position, converter feed pressure enters the release passage to release the clutch. The apply fluid bypasses the apply valve to the cooler passage.

When the TCC solenoid valve is ON, fluid can not exhaust through the solenoid. This allows TCC signal fluid pressure to move the converter clutch apply valve against spring force and line pressure. When shifted, the apply valve:

    • Directs regulated apply pressure from the converter clutch regulator valve into the apply passage which applies the clutch
    • Allows converter feed fluid to exhaust
    • Directs converter feed fluid into the cooler passage

When the TCC is applied, the clutch is nearly locked-up to the converter cover. This vehicle is equipped with an electronically controlled capacity clutch (ECCC) which controls TCC slip speed between -20 to +50 RPM to avoid noise, vibration and chuggle with TCC apply.

If the PCM detects 3 occurrences of TCC slip between -20 and +50 RPM for 5 seconds, when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type B DTC.

Conditions for Running 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 commanded gear is not 1st.
    • The transmission range selector position is 2nd, 3rd or 4th.
    • The throttle angle is 14-50%.
    • The engine torque is 95-271 N·m (70-200 lb ft).
    • The engine speed is 800-4,000 RPM.
    • The vehicle speed is 32-112 km/h (20-70 mph).
    • The speed ratio is 0.65-1.4.
    • The last range selector position change occurred more than 3 seconds ago.
    • The PCM has commanded the TCC OFF.

Conditions for Setting the DTC

DTC P0742 sets after 3 occurrences when TCC slip speed is -20 to +50 RPM, for 5 seconds each.

Action Taken When the DTC Sets

The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the conditions for setting the DTC exist.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
    • A scan tool clears the DTC from PCM history.
    • The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.

Diagnostic Aids
    • An engine stalling symptom may be present when a drive gear is engaged if the TCC is stuck on.
    • Inspect the transmission fluid and filter for sediment or debris.

Test Description

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

  1. A TCC slip speed in the range shown indicates that this DTC is current.

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. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM.

  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Start and run the vehicle.
  6. Select TCC Slip Speed on the scan tool.
  7. 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 +50 RPM

Go to Step 3

Go to Diagnostic Aids

3
  1. Perform the transmission fluid checking procedure. Refer to Transmission Fluid Check .
  2. Inspect for the following conditions:
    3. • The orificed TCC filter is damaged or missing from channel.
    • The TCC apply valve stuck ON because of sediment or damage.
    • The TCC solenoid valve stuck ON because of sediment or damage. Refer to Shift Solenoid Leak Test .
    • Refer to Control Valve Body Inspection in Unit Repair.

Was a condition found and corrected?

--

Go to Step 4

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4

Perform the following in order to verify the repair:

  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 engine speed is 800-4,000 RPM.
    • The vehicle speed is 32-112 km/h (20-70 mph).
    • The speed ratio is 0.65-1.18.
    • The last gear change occurred more than 3 seconds ago.
    • The PCM commands the TCC OFF.
    • The TCC slip speed is 150-2,000 RPM for 4 seconds.
  4. Select Specific DTC.
  5. Enter DTC P0742.

Has the test run and passed?

--

System OK

Go to Step 1