Automatic transmission selector position sensor AL4
Purpose:
The AL4 automatic transmission selector position sensor (also known as the range sensor) detects the position of the gear selector in the automatic transmission. This information is necessary for the transmission to operate correctly as it is used to:
* Definitions of the gear ratio to be included
* Torque converter lockup control
*Provide kick-down function
Location:
The AL4 automatic transmission selector position sensor is usually located on the gearbox housing next to the gear selector.
Device:
The selector position sensor is usually a potentiometer (variable resistor), which consists of:
* Fixed contact (sometimes called common contact)
* Moving contact (sometimes called sliding contact)
* A resistive element that connects the two contacts
As the gear selector moves through its various positions, the moving contact moves across the resistive element, changing the resistance between the fixed and moving contacts.
Working principle:
* When the gear selector is in any of the ranges (P, R, N, D, 3, 2, 1), the moving contact is in contact with the corresponding part of the resistive element, creating a certain resistance.
* This resistance is transmitted to the electronic control unit (ECU) of the automatic transmission.
* The ECU uses this resistance to determine the selected range and control the transmission accordingly.
Symptoms of malfunction:
A malfunction of the AL4 automatic transmission selector position sensor can cause various symptoms, including:
* Inability to change gears
*Hard or delayed gear shifting
* Incorrect torque converter locking
*No kick-down function
Diagnostics:
Diagnostics of the AL4 automatic transmission selector position sensor usually includes the following steps:
* Read fault codes
* Checking the sensor resistance in each gear selector position
*Checking sensor wiring and connections
Replacement:
If the selector position sensor is faulty, it must be replaced with a new one. The replacement procedure may vary depending on the specific vehicle model. However, in general it includes the following steps:
* Battery disconnection
* Removing the air filter
* Disconnecting the shift cable
* Disconnecting the sensor connector
* Unscrewing the sensor
* Installation of a new sensor
*Connecting the sensor connector
* Gear shift cable connection
* Air filter installation
* Battery connection