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Post by steveX » Sun Apr 20, 2008 5:13 pm

Vehicle Speed Sensor (VSS)) The vehicle speed sensor (VSS) sends a pulsing voltage signal to the ECM which the ECM converts to miles per hour. This sensor mainly controls the operation of the TCC system. There are several different types of vehicle speed sensor

PURPOSE The torque converter clutch (TCC) system uses a solenoid operation valve in the automatic transaxle to couple the engine flywheel to the input shaft of the transaxle through the torque converter, increasing fuel economy. (automatic transmission consume more fuel than Manual shift transmission).

OPERATIONFor the converter clutch to apply two condition must be met:

* Internal transaxle fluid pressure must be correct. This section will cover only the electrical operation of the TCC system.
* the ECM grounds a switch internally to turn "ON" a solenoid in the transaxle. this moves a check ball, which will allow the torque converter clutch to apply, if the hydraulic pressure is incorrect, as described above.

The ECM controls the TCC apply solenoid by looking at several sensors:
* VSS. speed must be above a certain value before the clutch can apply.
* Coolant temperature sensor. Engine must be warmed up before clutch can apply.
* Throttle position sensor (TPS). After the converter clutch applies, the ECM uses the information from the TPS to release the clutch when the car is accelerating or decelerating at a certain rate.
* GEAR Switch. 440-t4 transaxle use a 2nd,3rd and 4th gear discrete switch to send a signal to the ECM telling it which gear the transaxle is in. The ECM uses this information to very the conditions under which the TCC applies or releases.
* Another switch used in the TCC sircuit is a brake switch which opens the 12 volt supply to the TCC solenoid when the brake is depressed.

Results of incorrect operationIf the converter clutch does not apply, fuel economy may be lower than expected. If the vehicle speed sensor fails, the TCC will not apply. If the vehicle speed sensor fails, the TCC will not apply. if the 2nd 3rd or 4th gear switch does not operate, the TCC may not apply at the right time.
the torque converter clutch (TCC) system has different operation characteristics than an automatic transaxle without TCC. if the driver complains of a "chuggle" or "surge" condition, the car should be road tested and compared to a similar car to see if a real problem exists. Another TCC complaint may be a downshift felt when going up a grade, especially with cruise control. this may be clutch disengagement rather than a down shift, due to the change in TPS to maintain cruising speed. the owner`s manual section on TCC operation should be reviewed with the driver.

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