[98SteedaGT]

Being a computer tech, that sounds like something electrical in the Computer loop. If it instantly goes out when the Scan Tool is plugged in, it should be something in the computer. When the scanner goes to interface with the on-board computer it's probably sending it some type of coding that turns off the signal to that light, or makes the computer go into a diagnostic mode for a little while. Too bad you can't interface a TCP/IP packet sniffer and analyze the data being TX/RX on the wire in raw format..... Then you would know exaclty what's going on... Prob has something to do with Ford using Motorola CPU's instead of AMD... maybe you should load Linux into the computer, it might work better