00 vw golf problem

i installed a new deck in a 2000 vr6 gti. the radio works fine , but the problem i have is that after the install the check engine light came on. ive heard of something called a kay wire behind the radio that can cause this problem is this true? if so how can i fix this problem, if not, is there a solution for this check engine light problem? thanks in advance.mark brasil, alpine 9811, ppi 6600 6ch amp, planet audio comp. set(2), custom built slot portbox,3-4yr old audiobahn alum q 10",ppi 1000 watt amp, 04 scion xa

unfortunatly no i did not disconnect the battery before the install, but would it be possible to reset the computer after the install has been done, by disconneting the battery?mark brasil, alpine 9811, ppi 6600 6ch amp, planet audio comp. set(2), custom built slot portbox,3-4yr old audiobahn alum q 10",ppi 1000 watt amp, 04 scion xa

also the car had an aftermarket deck already installed in it. it was some cheap sony and we put in an alpine 9855.mark brasil, alpine 9811, ppi 6600 6ch amp, planet audio comp. set(2), custom built slot portbox,3-4yr old audiobahn alum q 10",ppi 1000 watt amp, 04 scion xa

no i did not disconnect the battery before the install, but the car already had an aftermarket deck put in it (some cheap sony) and we put in an alpine 9855.  would reseting the computer by diconnecting the battery work?mark brasil, alpine 9811, ppi 6600 6ch amp, planet audio comp. set(2), custom built slot portbox,3-4yr old audiobahn alum q 10",ppi 1000 watt amp, 04 scion xa