I was given a GM Tech II tool a number of years ago. It has been functioning just fine, until recently. Every time I have it connected to a vehicle that requires the CANDi attachment, I get a "No Communication....." error. I've googled the problem and don't seem to be able to get a real answer other than "Maybes.........." Thing works fine on cars that don't require the CANDi................

Did the Candi attachment work before on vehicles requiring it?

Try it on another vehicle?

I may be parsing the wording too closely, however: Do you have the CANDi module?