DTC P0742. Chevrolet Equinox 2005

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2005 🢒 Equinox 🢒 Brakes 🢒 Park Brake 🢒 DTC P0742

Circuit 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 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 A 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 TR switch DTC P0705.

•	No TFT DTCs P0711, P0712 or P0713.

•	No ISS DTC P0717.

•	No OSS DTC P0722.

•	No engine speed DTC P0727

•	No solenoid DTCs P0962, P0963, P0966, P0967, P0970, P0971, P0973, P0974, P0976, P0977, P0979, P0980, P0982, P0985 or P0986.

•	No engine torque DTC P1781.

•	No throttle position DTC P1791.

•	No CAN DTCs U2104 or U2105.

•	The ignition voltage is 10.5-18 volts.

•	The ignition is ON for 3.0 minutes or greater.

•	The selected gear range is Drive, Intermediate, or Low for 8 seconds.

•	The transmission fluid temperature is 20°C (68°F) or greater.

•	Not in Trans. Protection Mode.

•	The engine speed is 400 RPM or greater.

•	The engine torque is 46-240 N·m (25-177 lb ft).

•	The transmission is not in 1st or 2nd gear and the gear ratio is 0.73:1 to 2.27:1.

•	The Transmission ISS is not greater than 3000 RPM.

Conditions for Setting the DTC

The following conditions occur twice in one ignition cycle:

•	The TCM commands the TCC OFF.

•	The TCC slip is between -50 to +50 RPM for 12 seconds or greater.

Action Taken When the DTC Sets

•	The TCM requests the powertrain control module (PCM) to illuminate the malfunction indicator lamp (MIL).

•	The TCM turns the Trans. Protection Mode ON. When the Trans. Protection Mode is ON, the following conditions occur:

-	The transmission will operate in 5th gear when the transmission is shifted into D or I range and 2nd gear when shifted into L range.

-	The line pressure is at maximum.

-	The torque converter clutch (TCC) is disabled.

-	The TCM freezes the transmission adaptive functions.

•	The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.

•	The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as a Freeze Frame.

•	The TCM stores DTC P0742 in TCM history.

Conditions for Clearing the MIL/DTC

•	The PCM 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 an 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.

This step determines if the ISS signal is skewed by a large factor.

Step

Action

Values

Yes

Did you perform the Diagnostic System Check - Vehicle in Vehicle DTC Information?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Inspect for correct transmission fluid level. Refer to Transmission Fluid Check .

Is the transmission fluid level correct?

Go to Step 4

Go to Step 3

Visually inspect the transmission cooling system for fluid leaks. Refer to Fluid Leak Diagnosis .
Repair leaks as necessary.
Fill the transmission to the proper fluid level.

Did you find and correct the condition?

Go to Step 15

Go to Step 4

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

Important:

•	Before clearing the DTC, use the scan tool in order to record the PCM Freeze Frame and the TCM Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Freeze Frame and Failure Records from the PCM and the TCM.

•	Using the Clear Eng./Trans. DTC Info function erases stored DTCs in both the PCM and TCM.

Record the DTC Failure Records.
Clear the DTC.
Use the scan tool snapshot mode in order to record Commanded Gear, TCC PC Sol. Ref Current, and TCC Slip Speed.
Drive the vehicle in DRIVE (D) and record the TCC Slip Speed in 3rd, 4th, and 5th gears, under heavy throttle, when the TCC PC Sol. Ref Current is less than 100 mA.

Is the TCC Slip Speed less than the specified value?

50 RPM

Go to Step 5

Go to Intermittent Conditions in Engine Controls - 3.4L

Stop the vehicle and apply the parking brake.
Place the gear selector in PARK (P).
Allow the engine to idle.
Observe Transmission ISS with a scan tool.

Is Transmission ISS within the specified range?

400-800 RPM

Go to Step 6

Go to Step 11

Test for correct line pressure. Refer to Line Pressure Check .

Is the action complete?

Go to Step 7

Remove the control valve body cover (29). Refer to Control Valve Body Cover Removal in Unit Repair.
Inspect the inside of the control valve body cover (29) for excessive sediment.

Did you find excessive amounts of sediment?

Go to Step 10

Go to Step 8

Inspect the control valve body assembly (39) for the following conditions:

•	Stuck lock up relay valve (415)

•	Stuck lock up control valve (454)

•	Stuck TCC check valve (450)

•	Stuck secondary regulator valve (436)

•	Stuck solenoid relay valve (378)

•	Stuck TCC lock up PC solenoid valve assembly (SLU) (339)

Refer to Control Valve Rear Body Disassemble and Control Valve Body Disassemble - Middle in Unit Repair.

Did you find any of the above conditions?

Go to Step 12

Go to Step 9

Has the control valve body been serviced within the past 3 months or 4 828 km (3,000 miles)?

Go to Step 10

Go to Step 12

Inspect the following items:

•	Torque converter assembly (1)

•	Input shaft (567)

•	Fluid pump stator shaft assembly (208)

Refer to Torque Converter Assembly Removal , Forward and Direct Clutch Assembly Assemble , and Transmission Fluid Pump Cleaning and Inspection in Unit Repair.

Is the action complete?

Go to Step 13

Replace the input shaft speed sensor (73). Refer to Input Speed Sensor Replacement .

Is the replacement complete?

Go to Step 15

Repair or replace the control valve body assembly (39). Refer to Control Valve Body Replacement .

Is the action complete?

Go to Step 15

Repair or replace the transmission. Refer to Transmission Replacement .

Is the action complete?

Go to Step 14

Replace the transmission fluid. Refer to Transmission Fluid Replacement .
Inspect for the correct level of transmission fluid.
Add new fluid as necessary.

Important: The Reset Trans Adapts function will clear all adapt cells. This may affect transmission performance. The TCM will update the adapt cell values as the vehicle is driven.

Use the scan tool in order to perform the following:

•	Reset the oil life monitor to 100 percent.

•	Reset Trans Adapts.

Did you complete the above procedures?

Go to Step 15

Perform the following procedure in order to verify the repair:

Select DTC.
Select Clear Info.
Operate the vehicle.
Select Specific DTC.
Enter DTC P0742.

Does the DTC reset?

Go to Step 2

Go to Step 16

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 in Vehicle DTC Information

System OK