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.
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 engine run time is 5 seconds 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 34-240 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 ECM 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 ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame. |
| • | The TCM stores DTC P0742 in TCM history. |
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. |
| • | 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.
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.0L (L81) | ||||||||||||
2 | 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 | ||||||||||||
3 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 4 | ||||||||||||
4 |
Important:
Is the TCC Slip Speed less than the specified value? | 50 RPM | Go to Step 5 | Go to Intermittent Conditions in Engine Controls - 3.0L (L81) | ||||||||||||
Is Transmission ISS within the specified range? | 400-800 RPM | Go to Step 6 | Go to Step 11 | |||||||||||||
6 | Test for correct line pressure. Refer to Line Pressure Check . Is the action complete? | -- | Go to Step 7 | -- | ||||||||||||
7 |
Did you find excessive amounts of sediment? | -- | Go to Step 10 | Go to Step 8 | ||||||||||||
8 | Inspect the control valve body assembly (39) for the following conditions:
Refer to Control Valve Rear Body Disassemble and Control Valve Body Disassemble - Middle . Did you find any of the above conditions? | -- | Go to Step 12 | Go to Step 9 | ||||||||||||
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 | ||||||||||||
10 | Inspect the following items:
Refer to Torque Converter Assembly Removal , Forward and Direct Clutch Assembly Assemble , and Transmission Fluid Pump Cleaning and Inspection . Is the action complete? | -- | Go to Step 13 | -- | ||||||||||||
11 | Replace the input shaft speed sensor (73). Refer to Input Speed Sensor Replacement . Is the replacement complete? | -- | Go to Step 15 | -- | ||||||||||||
12 | Repair or replace the control valve body assembly (39). Refer to Control Valve Body Replacement . Is the action complete? | -- | Go to Step 15 | -- | ||||||||||||
13 | Repair or replace the transmission. Refer to Transmission Replacement . Is the action complete? | -- | Go to Step 14 | -- | ||||||||||||
14 |
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.
Did you complete the above procedures? | -- | Go to Step 15 | -- | ||||||||||||
15 | Perform the following procedure in order to verify the repair:
Does the DTC reset? | -- | Go to Step 2 | Go to Step 16 | ||||||||||||
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 in Engine Controls - 3.0L (L81) | System OK |
