Thread: OBD2 Port not Working with Scan Tool

Hello all,

I have a 2004 Grand Prix GT with 85K original miles. I absolutely love the car and want it to last as long as possible. Recently my check engine light came on, however, the OBD2 port is not allowing a scan tool to read the codes. I've tried my personal scan tool, Autozone and Advanced Auto scan tools - none will read the codes. I then went into my fuses to check the "auxiliary power" fuse to ensure it was not blown. The fuse is good. What else can I do to determine what the problem is? I'd prefer to stay away from the dealership at all costs because I know they will charge me a ton of money to even look at the car. Any thoughts or ideas is greatly appreciated!

Thanks!

I believe the CIG light fuse is the auxiliary power fuse on the 04 GT. Regardless, my cigarette lighter outlet functions properly. I was sure it had to be a blown fuse, but now this has me really stumped.

Check the fuse for the OnStar feature, even if yours doesn't have that feature.

The car did have OnStar at one point and time (when my parents owned it). I went and checked the Onstar/Diagnostic Link fuse, and sure enough it was missing. I will put a new fuse in and see what happens.

Thanks!