The hall sensor (6501KW2002A) on the LG front load washing machines is located on the bottom back side of the stator. Unplug the washer, then to access it you have to remove the back panel of the washer, remove the rotor (single large bolt), then remove the stator (6 smaller bolts), unplug the two connectors and remove the ground and you can pull the stator off to access the hall sensor. The hall sensor just clips on, so you just have to unclip the old one and clip on the new one.
The Hall Sensor is a Rotor Position Sensor (RPS), it tells the computer what position the rotor is in. The computer uses this to see how fast the drum is spinning along with other things. When the Hall Sensor goes bad, it will commonly give an LE error (Locked Rotor error) on the washer. When the sensor goes bad it can cause the drum not to drum properly and even make the washer make some strange growling noises.
If you have any questions, post them in the comments below. If you need to purchase a Hall Sensor for your LG washer, visit the link below.