98z28darkhell

I Installed a new ECT sensor on my camaro beacuse my guage was not reading a temp. The actual guage its sellf works beacuse when i turn the car on and off it moves. But when the car is running the guage will not work. I looked on all data and ran through all the test they asked me to. When i use the snap on modis and jump the wires the temp goes from -38 to 238 like its suspose to. So the wiring is good and the the cars computer is reading it. So the wiring and the computer and the sensor are not bad. My buddy has the same year camaro as me i took his ECT sensor out and put it in my car and it still didnt work. I also put mine on his and it did work. So it something to do with my car. The wiring is good the sensor is good and and Cars ECU is good. Has anyone else had this proble or know what is wrong?