Volkswagen Repair: vw jetta, vw jetta, stereo installer

Question
I have a 99.5 (new) jetta. My son put a new radio/cd player in the car shortly after we got it. Now it won't pass the Maryland State Emission test. I took it to the dealer and they said that all the communications for the car are run through the radio, and that is why it keeps failing the test since the exaust system is fine. I no longer have the original radio. Have you ever heard of this happening? If I go to a junk yard and buy a vw radio will it be able to communicate? Now the keyless entry won't work and when we try to start the car the alarm sounds as soon as we put the key in. I'm wondering if all of this is connected. This car has been a nightmare from day one but unfortunately I can't get rid of it. Thanks for your help.

Answer
Lisa, thank you for your question.  My first reaction was “someone is full of it”.  But after doing some additional checking, it is true.  The computer is connected to radio by the “K” wire.  Getting a radio from a 1999 Jetta should take care of the problem.  I can not say if there is a way of connecting that wire up to the new radio (the radio that is currently installed), of what will happen.  If you connect that wire to the current radio, my best guess is the computer will short out and then you are talking serious money.  My suggestion is to get a radio fro a 99 Jetta and replace the currently installed radio. Should he want a different radio in the car, I also suggest taking it (or calling) somewhere like Car Toys or any other reputable alarm and stereo installer.  
here is some additional information that might be helpful: What is the K-Wire?


The K-wire is a data bus that goes between the hu and the ecu. Most everything in the newer cars are linked to the ecu, via a K-wire. If for example the right front woofer was disconnected, the ecu will know about it. If you connect a scan tool to the ecu and address the headunit, it will tell you that the right front woofer is disconnected. All the K-wire is is a communications path. When you hook up an aftermarket headunit, the K-wire is no longer necessary. If the K-wire is connected to anything, even to itself, it will cause problems for the ecu, and possibly damage the scan tool as well. When you hook up an after market headunit, be sure that the harness adapter you use has no wires that are looped.That is,a wire that has both ends connected to the adapter.If you find this,either cut the looped wire(s)and tape them up,or yank the looped wire(s)right out of the adapter.If you choose not to use an adapter,then simply leave the K-wire connected to the unused factory connector.

Hope that helps