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 powertrain control module (PCM) begins the TCC duty cycle at approximately 42 percent. The PCM 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 PCM 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 PCM recognizes that the TCC is no longer engaged.
When the PCM 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 this DTC:
DTC P0742 Torque Converter Clutch (TCC) System - Stuck On

Conditions for Running the DTC
^ No MAP DTCs P0107 or P0108.
^ No TP DTCs P0122 or P0123.
^ No TCC release switch DTC P1887.
^ No TCC electrical DTC P2761.
^ The TFP manual valve position switch indicates DRIVE.
^ The transmission fluid temperature is 10 - 130°C (50 - 266°F).
^ The TP angle is 12 percent or greater.
^ The engine torque is greater than 27 Nm (20 ft. lbs.).
^ The TCC is commanded OFF.

Conditions for Setting the DTC
The TCC release switch is closed, release fluid pressure not present, for 4 seconds, 4 times during the same trip.

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
^ The PCM commands TCC engagement.
^ The PCM commands maximum line pressure.
^ The PCM freezes transmission adaptive functions.
^ The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
^ The PCM stores DTC P0742 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
^ The PCM 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 PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

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 PCM, the TFP manual valve position switch and all other circuit connecting points for an intermittent condition.
^ Inspect the circuit wiring for an intermittent condition.
^ The customer may notice an engine stalling condition.

Test Description








These numbers 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 PCM should recognize an open TCC release switch. This indicates the wiring from the AT inline 20-way connector to the PCM 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.