Did you use the wires given to you when you got the subwoofer and amplifier? If you've used the wires already there than you haven't got a big problem. Always use the wires that come with the kit or you will always have some problem! I've tried it before on my focus and I had the exact same problem!So after installing an aftermarket amp and sub, all the controls on my steering wheel including turn signals and wipers stopped working. I've gone through all the fuses and they're all good. Any ideas?