My 2006 LBZ just went into limp mode! My Helm's manuals haven't arrived, and the dealer is being uncooperative regarding scheduling. The truck was running fine this morning. the second start of the day the CEL light came on and now the truck is holding the RPM up and shifting funny any suggestions as to where to start looking would be greatly appreciated.

I do realize that there is not much to go on. So thanks

The truck is bone stock, no mods whatsoever and only has 75000km on it.