Strang electrical problem - please help

I have a 97 Z28. I installed an electric exhaust cutout and it worked fine for 2 days then stopped working. I got power and ground from the unused connector next to the driving light switch. I think it was used for traction control.

anyway to make a long story short:

The ground I used no longer is a ground.

What could cause this?

BTW, the color wires I used were:

12V = Brown
Gnd = Grey

Thanks

Just ground it to the car... You did fuse the 12v right?

Thanks.

I already did that and it works fine now. I just wasn't thinking right when I installed it and used the ground that was at the connector.

I was just curious what could have happened for that wire not act as a ground anymore.

By the way, I did use a meter and have installed many a car stereo. I just F'ed this up some how.

Thanks again.