Yes, first thing to check is any external sensor, dirt can cause a bad connection, stones can damage wiring and the worst culprit of all is a high pressure wash under the car.
Originally Posted by Naka
Sensors can also be hidden behind protective plates so look carefully.
What is your car? Sometimes it's cheaper in the long run to change the gearbox as repairs can be expensive.
Last time i had a problem with a BMW gearbox the dealer said never change gearbox oil or you will have nothing but problems.
So i changed the oil, what a huge mistake.
But O, how bitter a thing it is to look into happiness through another man's eyes.