Automatic transmission selector position switch (automatic gearbox)
This is an electronic sensor that is installed on the gear shift lever and transmits information to the electronic transmission control unit (ETCU) about the selected position of the automatic transmission selector.
Working principle:
* Inside the selector position switch there is a movable contact that moves in accordance with the position of the automatic transmission selector.
* When the selector is moved to a certain position, the moving contact comes into contact with the corresponding fixed contact.
* This completes the electrical circuit, sending a signal to the computer.
Functions:
* Informs the computer about the selected position of the automatic transmission selector.
* Allows the ECM to activate the appropriate torque converter gears and lock-ups.
* Prevents the engine from starting if the automatic transmission selector is not in the Park or Neutral position.
Main types of automatic transmission selector position switches:
* Mechanical: Used in early automatic transmissions and directly connected to the gear lever.
* Electronic: Used in modern automatic transmissions and convert the selector position into electrical signals.
Symptoms of malfunction:
* Difficulty shifting gears.
* The correct position of the selector lever on the instrument panel is not displayed.
* The engine cannot be started if the selector lever is not in the Park or Neutral position.
Causes of malfunction:
* Worn or damaged contacts.
* Electrical wiring fault.
* Incorrect adjustment.
* ECU failure.