DomsLT1

I had my opti replaced because my car wouldn't start, so the mechanic said that he was gonna test the security system, but when he went to test it, it was already unplugged. Well I got the car back and he must have left it unplugged because the light never comes on. Also The light has NEVER came on for me since I had the car. What does he mean it was unplugged and how do i plug it back in? Is there a reason the previous owner unplugged it? Thanks!!!!