Well, Jimmy's back at the repair shop. They hooked up a GMC scanner to it the other day with no problem until my kid tried to drive it home. They're going to scan it again now that the SES light is on with the P0441 code. I don't know if the the GM scanner is going to give them any more information. The first mechanic I took it to suspected the valve (they replaced the hose so that should be okay).
drdd - I have no idea if it has CPI. We've only had the truck three weeks.