installed stereo and car want turn over

[absmith]

ok fitted a cd player to my vr statesman but now the car wont start the old tape deck thing had the security thing in it so wen u diconect the battery u have to type in a pin to get it back but u could still start the car u just had no music
now i've fitted just a basic pioneer cd player without using the stereo controls on the steering wheel but i'm left with a black cable like the areial cable that was plugged into the factory unit is this a security cable or wat

any ideas help would be good

[bodybodyrock]

ohh man i have no idea wat uve done, ide say start with basics see if all the fuses are good coz u might have blown one puting stereo in