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Makes 🢒 Cadillac 🢒 2007 🢒 DTS 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T80-E 🢒 DTC P0742

Object Number: 25443 Size: SF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The transmission control module (TCM) controls the torque converter clutch (TCC) solenoid valve pulse width modulation (PWM). The solenoid controls the hydraulic fluid for TCC apply and release. When the vehicle is accelerating, the TCM commands the TCC to be disengaged.

If the TCM detects a low TCC slip from -20 to +400 RPM, 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 MAF DTCs P0101, P0102 or P0103.
    • No MAP DTCs P0106, P0107 or P0108.
    • No TP DTCs P0121, P0122 or P0123.
    • No OSS DTCs P0722 or P0723.
    • No AT ISS DTCs P0716 or P0717.
    • No TCC stuck OFF DTC P0741.
    • The engine run time is greater than 5 seconds.
    • The transmission gear ratio indicates 3rd or 4th gear.
    • The transmission fluid temperature is 20-130°C (68-266°F).
    • The TP angle is 8-90 percent.
    • The engine torque is 50-1492 N·m (37-1100 lb ft).
    • The vehicle speed is 16-51 km/h (10-32 mph).
    • The TCC is commanded OFF.

Conditions for Setting the DTC

The TCC slip speed is -20 to +400 RPM for 4 seconds, 4 times during the same ignition cycle.

Action Taken When the DTC Sets
    • The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
    • The TCM commands maximum line pressure.
    • The TCM forces TCC application.
    • 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 and 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 during the second consecutive trip in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
    • The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
    • The TCM clears the DIC message when the condition no longer exists.
    • A scan tool can clear the MIL/DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the ignition switch 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.
    • Potentially DTC P0742 can false fail and may have been set due to another DTC.

Test Description

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

  1. This step verified that the TCM commanded the TCC PWM solenoid valve OFF and the slip speed is -20 to +400 RPM.

    2.

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

DTC P0742

Step

Action

Values

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

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 Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the 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 D4, while in 4th gear command a TP angle greater than 8%.

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

-20 to +400 RPM

Go to Step 3

Go to Diagnostic Aids

3

  1. Inspect for the following conditions:
    2. • The TCC PWM solenoid valve is stuck ON due to sediment.
    • The TCC converter feed limit valve is stuck ON due to sediment.
  2. Repair or replace any malfunctioning component.

Did you complete the repair?

--

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 D4 with a TP angle of 8-90% and a vehicle speed greater than 16 km/h (10 mph).
    • The TFT is 20-130°C (68-266°F).
    • The engine torque is 50-1492 N·m (37-1100 lb ft).
    • The TCC slip speed must be 150-1,500 RPM for 3.5 seconds.
  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?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK