Signs of malfunction and failure of the transmission position sensor (switch)
The main signs of the transmission position sensor malfunction are as follows: the engine does not start, the car does not move, the transmission switches to another gear when a certain gear is switched on, and the transmission goes into emergency mode.
The transmission position sensor, also called the transmission range sensor, is an electronic sensor that provides a signal about the gear selected by the driver to the transmission control unit (TCU). This means that the TCU controls the transmission shift according to the command given by this sensor.
Over time, the transmission range sensor fails or wears out. There is a number of signs indicating this malfunction or failure.
1. The Engine does not start, the car does not move.
Without receiving the “Parking/neutral” signal provided by the transmission range sensor, the TCU will not be able to signal the engine to start. That is, under these conditions, it is impossible to start the car engine. In addition, if the transmission range sensor fails, the TCU stops recognizing any incoming transmission signals. Therefore, in this case, the car just will not budge.
2. When you enable a given gear, the transmission is switched to another gear.
Sometimes, when the selector lever is moved to a certain position, the sensor signals a completely different gear. As a result, the TCU is controllably switched to a gear that does not correspond to the one selected by the driver using the selector lever. This is dangerous because it reduces the level of safety when driving and increases the likelihood of getting into an accident.
3. Transmission goes into emergency mode.
Some vehicles have the following feature: if the transmission range sensor fails, it will still be possible to turn on the transmission mechanically, but the TCU will not receive any data about this transmission. For safety reasons, a hydraulic or mechanical transmission lock is provided on one of the gears. This mode of operation of the transmission is called emergency mode. Depending on the manufacturer and the specific transmission version, the emergency mode may involve the third gear, fourth gear, or fifth gear, as well as reverse gear.
Detection of any of these signs indicates the need to contact a mechanic.