There is no limp mode on a 4.9l, and if this is a Northstar, is there a check engine light that may provide an indication of why it would be in reduced power mode. I can find no definate answer on what limp mode strategy is, or why it occurs. I would be skeptical in not thinking that the vehicle has a system problem.
Friday, February 11th, 2011 AT 6:50 AM