For a temporary test you can bypass the seat switch while you operate it and test it, but MAKE SURE YOU CONNECT IT BACK. This will rule out the seat switch and wiring completely. If it still causes travel issues, I am sure the Neutral light is coming on then the truck doesn't travel. I would suspect that the OSS controller is faulty. Make sure you order the correct part # also as there are many and the numbers are only 1 digit difference.