We also have a 2005 C7. We had the same symptoms three years ago. When ever we stepped on it going up hill the alarms and stop engin lights would come on. As soon as we took our foot off they would stop. Ran perfectly except for that.
When we had it serviced they updated the engine codes. Good to go for the next year.
Two years ago it started again. Around 60,000 miles on the MH. Ran perfect until you stepped hard on the accelerator. Took it in, they ran a bunch of test and this time not so simple. Bearings going on the turbo, could last for another 50k or have a catastrophic failure causing more damage. We decided to have it fixed. Cost just over 4K, ouch. A year later it's still running great. No more alarms.
I did some reading and found a slew of folks that had the same issue with their C7. All in the 2004-2006 year range.
