Gear Position Sensor


Gear Position Sensor

If you have ever driven a vehicle with an automatic transmission, you should be aware of the steps required to start the engine. Your transmission must be in the park or neutral position and the brake pedal must be depressed. To keep this under control is the job of your gear position sensor. It monitors the position of the gear shift lever and sends this information to the control unit. In addition, it is responsible for activating the reverse lights when your vehicle is moving backward.


Depending on your vehicle, it can be equipped with a mechanical or electronic gear position sensor. If you drive a newer car or truck, most likely, it is equipped with a computer-controlled gear position sensor that doesn’t provide any physical connection between the shift lever and the transmission. This type of sensor relies on wires to inform the control unit about the position of the lever. Besides, it provides several additional safety functions by not allowing the driver to go into a lower gear at a high speed, and to shift into the park or neutral position if the car is moving forward.

A gear position sensor can be found in just about any newer vehicle with an automatic transmission. It is a crucial part of the transmission system, which can cause a number of problems if it malfunctions. Here are the most common of them:

Inability to start the vehicle

Your computer relies on the gear position sensor to determine the position of the shift lever. If the sensor fails, the computer will not allow you to start the vehicle to prevent it from damage.

You can’t shift into drive or reverse

This is an indicator of a malfunctioning gear sensor. It lets the computer know that the shift lever is in the park position, but doesn’t send any information to the control unit when you shift into drive. That’s why the latter doesn’t allow the transmission to go into the right gear.

Your transmission shifts into a wrong gear

If your gear position sensor sends incorrect data to the computer, it may cause the transmission to engage an incorrect gear, which can affect your safety and drivability. 

“Limp home” mode is activated

On newer vehicles equipped with a computer-controlled transmission, the operation of the sensor is monitored by the control unit. If it detects a malfunctioning sensor, it will activate the “limp home” mode, limiting your speed and the quantity of gears you may use. This is done to prevent the transmission from possible damage. 

Illuminated check engine light

If your engine control module detects a bad gear position sensor, it can turn on the check engine light to alert you of the problem. The sensor may also affect your emissions, resulting in a specific trouble code provided by the computer.

Can I drive my vehicle if the gear position sensor fails?

Driving a vehicle with a bad gear position sensor is not the best and safest driving experience you’d like to have. It’s better to get in touch with your mechanic to fix the sensor as soon as possible.

How can I fix a bad gear position sensor?

Before replacing a bad gear position sensor, its thorough diagnosis is recommended to avoid unnecessary labor and repairs. Your mechanic will read the trouble codes provided by the computer and analyze all available symptoms to determine the source of the problem. If the sensor needs a replacement, the mechanic will install a new gear position sensor and check its operation. 

It is always a good idea to check your transmission for any irregularities and fix them if necessary. Your fluid level should also be checked and topped up or replaced if needed to prolong the service life of the transmission and its components. This is your cost-effective investment into long-lasting trouble-free transmission operation. 

If you want to save some money, you could replace a gear position sensor yourself. However, you should leave this job to a professional if you don’t have proper mechanic skills or your vehicle is equipped with a computer-controlled sensor that involves complex troubleshooting of the transmission.

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