the issue that you are having could be the result of a bad ground connection that the wiring harness for the 2002 Pontiac Grand Am cannot overcome, but the one on the truck can.
Since vehicle manufacturers can use any wire color, they want for any function I cannot tell you which wire colors were used on your specific model. So, what we will have to do is test the wiring using a circuit tester such as # PTW2993.
Once you have determined the wire functions you can make the connections... view full answer...