There seems to be two levels of 'limp mode', when the computer's 'on board diagnostics' (OBD) reads that one or more sensors are out of a predetermined range it typically will not let you operate the unit at full power but still allows you to get home instead of leaving you stranded.
That said, I have had an unresolved intermittent problem that has caused me to go into a limp mode like I just described (and seems to be hour problem too Vic), AND I have had a more serious limp mode that won't let the engine go much off of an idle.
Hope that helps, if I get my issue(s) figured out I will be sure to reply with the solution mine needed seeing as there's almost no info for these machines anywhere online!