P0742
DTC P0742
Circuit Description
The torque converter clutch (TCC) solenoid valve is a pulse width modulation (PWM) solenoid. When vehicle operating conditions are appropriate for TCC application, the transmission control module (TCM) begins the TCC duty cycle at approximately 42 percent. The TCM then increases the duty cycle up to 90 percent, in order to achieve full TCC-apply pressure.
When the TCC PWM solenoid valve is de-energized, the solenoid blocks filtered 2-3 drive fluid, and allows TCC signal fluid to exhaust. When energized, the solenoid modulates fluid into the TCC signal fluid circuit. When fully energized, modulation stops, and the solenoid blocks both 2-3 drive fluid and TCC signal fluid exhaust.
The TCC release switch is part of the automatic transmission fluid pressure (TFP) manual valve position switch. The TFP manual valve position switch is attached to the control valve body.
The TCC release switch is a normally-closed switch. The switch signals the TCM that the TCC is released. Torque converter release fluid pressure acts on the switch contact, opening the signal circuit. When the voltage on the circuit is high, the TCM recognizes that the TCC is no longer engaged.
When the TCM detects that the TCC release switch is closed 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 MAP DTCs P0107 or P0108.
^ No TP DTCs P0120 or P0220.
^ No ISS DTCs P0716 or P0717.
^ No OSS DTCs P0722 or P0723.
^ No TCC stuck OFF DTC P0741.
^ The engine is running for 5 seconds.
^ The transmission fluid temperature (TFT) is 20°C to 130°C (68°F to 266°F).
^ The Calc. Throttle Position is between 8 percent and 90 percent.
^ The engine torque is greater than 50 N.m (37 lb ft).
^ The vehicle speed is greater than 16 km/h (10 mph).
^ The TCC is commanded OFF.
^ The gear ratio is between 0.63:1 and 1.74:1.
Conditions for Setting the DTC
The TCC slip speed is -20 RPM to +40 RPM, for 6 seconds, 3 times during the same trip.
Action Taken When the DTC Sets
^ The TCM illuminates 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 commands TCC engagement.
^ The TCM freezes transmission adaptive functions.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Freeze Frame and 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 TCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ 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 could set DTC P0742.
^ Inspect for a pressure regulator condition.
^ Inspect for abnormal high or low line pressure.
^ Inspect the connections at the TCM, the TFP manual valve position switch and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics
^ Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents. Component Tests and General Diagnostics
^ The customer may notice an engine stalling condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for a TCC release switch status change when the engine is running. If TCC release oil is present, the switch should be open.
4. If you disconnect the AT inline 20-way connector, the TCM should recognize an open TCC release switch. This indicates the wiring from the AT inline 20-way connector to the TCM is good.
7. This step ensures that the TCC release switch is in good working condition.
8. This step tests the TCC circuit for a mechanical or hydraulic condition.
