Hi all,

As some of you know, I had a trailer hitch installed on my 2005 GXP along with wiring for the lights. Service engine light came on the next day, and a GM Tech2 scanner won't communicate with the car. The tech at the dealership where I work thinks there'* a faulty connection somewhere that won't allow the scanner to communicate with the car. I know next to nothing about wiring, and have no idea what to look for when I pull it apart. I've checked the hot wire connection at the battery and taped up the connector block that was just flopping around loose under the seat. The other connections are at the left taillight and I haven't had a chance to pull it apart and check for anything obvious. Any thoughts would be greatly appreciated.

Oh, and if this weren't enough, when the hitch was installed, the exhaust had to be dropped at the rear to replace and reposition the hangers and during this process pulled the O2 sensor out from under the heat shield and the shield had cut the wires to the sensor and the heat shield was rubbing against the O2 sensor, making the most god awful noise you can imagine. $140 later, it was fixed at the dealership and the bill sent to the installer, who is making good on it.

I know I should just take it back to the installer and have him figure out where the fault is, but I'm just really not sure I trust him to be working on my car anymore at this point. Thanks.

Could have the dealer fix it and bill the installer if he'* not going to do the job right.

I wouldn't touch it if I were you, either take it back and let the installer figure it out maybe he can see his mistake or take it to the dealer and bill the installer (the installer should be aware of what you're doing BEFORE you drop it off at the dealer)
The second you start touching wires and playing with it, that will be the green light for the installer to say "oh you messed up by doing so and so" and throwing the lamest excuses ever.
I would ask them to re-check all the wiring, specially the ones they cut and re-fixed.
Good luck!

Problem fixed. Called installer today, explained problem, he knew exactly what it was. He removed a self-resetting breaker and put an inline fuse in it'* place. Went back to the dealer, hooked up the scanner,and voila! O2 sensor code. Cleared code, no more "service engine soon" light.

Well that was easy. I'll mark this as fixed just in case it comes up again.

glad you got it fixed, when usually when the problems start they never end lol