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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 5L40-E/5L50-E 🢒 DTC P0742

Object Number: 798826 Size: MF

Circuit Description

The transmission control module (TCM) controls the torque converter clutch (TCC) solenoid valve pulse width modulation (PWM). 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 and TCC slip speeds of -300 RPM to +1,500 RPM, during heavy acceleration, are normal.

If the TCM detects low torque converter slip when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type B DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

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

Conditions for Running the DTC
    • No TP sensor DTC P0120.
    • No ISS DTCs P0716 or P0717.
    • No OSS DTCs P0722 or P0723.
    • No TCC stuck OFF DTC P0741.
    • No IMS DTCs P1815, P1820, P1822, P1823, P1825 or P1826.
    • No engine torque signal circuit DTC P2637.
    • No TCC solenoid electrical DTCs P2763 or P2764.
    • The engine run time is greater than 5 seconds.
    • The IMS range is D5.
    • The transmission fluid temperature is 20-130°C (68-266°F).
    • The engine torque is greater than 80 N·m (59 lb ft).
    • The throttle position is 12-90 percent.
    • The transmission is not in 1st gear and the gear ratio is 0.73:1 to 2.27:1.
    • The vehicle speed is greater than 15 km/h (9 mph).

Conditions for Setting the DTC

The following conditions occur 4 times in one ignition cycle:

    • The TCM commands the TCC OFF.
    •  The TCC slip is between -20 to +20 RPM for greater than 3.5 seconds.

Action Taken When the DTC Sets
    • The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive drive trip in which the Conditions for Setting the DTC are met.
    • The TCM inhibits 5th gear when in Hot Mode.
    • The TCM freezes transmission adaptive functions.
    • The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
    • The TCM stores DTC P0742 in TCM history.

Conditions for Clearing the DTC
    • The ECM turns off the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
    • A scan tool can clear the DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non emission related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.

Diagnostic Aids
    • Rapid fluctuation in line pressure may set DTC P0742. Refer to Line Pressure Check .
    • The customer may notice an engine stalling condition.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step verifies that the TCM commanded the TCC PWM solenoid valve OFF and the slip speed is -20 to +150 RPM.

    2.

  2. This step inspects and repairs the components that caused the DTC to set.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. Important: 

       • Before clearing the DTC, use the scan tool in order to record the ECM Freeze Frame and the TCM Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the ECM and the TCM.
       • Using the Clear Info function erases stored DTCs in both the ECM and TCM.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Select TCC Duty Cycle and TCC Slip Speed on the scan tool.
  6. Drive the vehicle in D, with the throttle angle greater than 15 percent. Allow the transmission shift to 5th gear.

While the TCC duty cycle is 0 percent, does the scan tool display a TCC slip speed within the specified range?

-20 to +20 RPM

Go to Step 3

Go to Intermittent Conditions in Engine Controls - 3.6L or Intermittent Conditions in Engine Controls - 4.6L

3

  1. Inspect for the following conditions:
    2. • The TCC PWM solenoid valve (352) is stuck ON due to sediment.
    • The TCC regulator apply valve (348) is stuck due to sediment. Refer to Torque Converter Clutch Solenoid Replacement .
  2. Repair or replace components as necessary.

Did you find and correct a condition?

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Go to Step 4

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4

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • Drive the vehicle in D with the throttle angle of 15-90 percent and a vehicle speed greater than 15 km/h (9 mph).
    • The TFT is 20-130°C (68-266°F).
    • The engine torque is greater than 80 N·m (59 lb ft).
    • The TCC slip speed must be 130-1,500 RPM for 2.5 seconds.
    • Stop the vehicle.
    • Drive the vehicle, as noted in Steps 1-3 above, in order to cycle the TCC a second time.
  4. Select Specific DTC.
  5. Enter DTC P0742.

Has the test run and passed?

--

Go to Step 5

Go to Step 2

5

With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

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Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK