I have a 2006 Monterey with a 400hp C9 engine. While driving I70 from Glenwood Springs to Denver (three long climbs) I seemed to notice that engine was laboring until I manually downshifted, both uphill and also when back down to bottom. Engine seems to perform OK when not under load, but when accelerating, it struggles. During operation water and trans temps were normal; check engine light did not illuminate. After parking, I checked all fluid levels (OK) and then attempted to run both trans and engine diagnostics. Transmission reported no diagnostics, running d1 through d5. I also drained some fuel from the filter bowl and noticed dirt particles in the fuel.
I then tried to run engine diagnostics and continue to get the following: 2 blinks, slight pause, 5 blinks; after a few seconds, 1 blink, slight pause, 6 blinks; after a few seconds, 1 blink, slight pause 6 blinks. After about a five second pause the same sequence repeats.
I can not relate the above to the diagnostic charts in my CAT operation manual.