aftermarket stereo results in computer readout failure. no fix from VW…help
VW has sent out warnings that incorrect radio installation will cause damage to there scan tools. The recommended procedure is to remove the radio prior to diagnosis.
Late model VWs do suffer with communication bus problems when aftermarket hifi equipment is installed, note these problems can result in other component failures.
Take a look here : http://www.ross-tech.com/vag-com/aftermarket-radio.html