I have a 2003 Audi A4 and I am installing a Pioneer Avic-Z3 Navigation Unit. I unplugged the blue harness plug at the instrument cluster and clamped the brown and red speed sensor wire for the GPS. When I plugged the harness back in, and tried to turn on the car, the car turned on, but won't stay on for more than about 2 seconds. Does anyone know how to fix this problem? Please let me know if you do...

 

You must have crancked the engine with the plug diconnected. The immobiliser is now blocked. You need to visita dealer.