1995 Mustang stereo problem.

I just replaced my stock stereo unit on my 1995 V6 Mustang. It originally came with a cassette/radio with the premium sound option, and I replaced it with a Pioneer mp3/cd unit. The installation wasn't too much of a problem. I cut the factory plugs, stripped the wires and, since I had a factory schematic, wired it up alright, and the stereo itself works fine. At first, I didn't know it had an external amp, so I eventually fixed that problem as well. However, I DID end up with two unused wires: one is the dimmer for the factory stereo lights, the other is probably the ground for the external amp.

My problem is, the check engine light and air bag warning lights have been coming on about a day after I installed the new unit. At first, I thought it could be bad connections since I didn't use a fastener or wire nut. So, I then pulled it back out, fastened the wires with crimp nuts and, suspecting that the problem also could have been the unconnected "ground" from the external amp, attached that to the other ground wires. Unfortunately, that didn't fix the lights either. So, any ideas? I can't be 100% sure that these lights didn't come on before the install, as I've only had the car for about a month probably, but they never came on once before, and these lights have a relative frequency of coming on.

that should'nt have anything to do with the raido,but next time never cut factory harness go to best buy and buy a wiring harness its alot easier and they come with the plugs to buy pass the factory amp.

My impatience gets the best of me sometimes. But the actual stereo still works like a charm.