My 05 Topkick came w/out the trans temp gauge. I purchased one from my local dealer. Behind the cut out there is a harness for it which seems to work due to the lights coming on when plugged in, but the needle does not move. Maybe it's not getting hot enough or do I need to add the sensor for it? Does the same sensor for the computer also control the gauge? If I need to add the sensor, where does it go? The dealership couldn't help me. Thanks