OBD Problem
 

'04 CTS, 3.6
Engine light is on, my scan tool reads ""Link Error". Tested scan tool on other cars, reads OK.

Sounds like an ECM problem. Any ideas?

Sound like data line fault, try Tech2 see if will scan it. ECM would be a guess. What is the concern you have?

My concern, of course, is the engine light being on. The radio screen gives intermittent massages, check gas cap (fine), check coolant level (full)
Tech2 will be my dealer option, and I guess that's the best way to diagnose the problem, or problems.