Originally Posted by
JockD
If the switch does not fix the problem, then there may be a contact sticking within the GEM. This is a real problem, since I have not found a source that repairs the GEM, and Ford wants an arm and a leg for a new one, and any GEM installed in your truck has to be reprogrammed to match your truck by a dealer or someone with a very advanced scanner/programmer.
The Gem could be getting wet as reax states but unless there have been changes in later model years the gem does not have to be reprogrammed, you have to buy one that is for your truck but it is a replace and drive item, dealer not needed other to get the part. If you truck is a 2wd I may have a new gem for your truck. I'm not sure if they are different from gas to diesel.