There are a few different types of limp modes.. one is the TCM limp which we discussed and then there is Throttle body limp mode where the TPS in the throttle body doesnt like what it see's and basicly does the same thing the TCM limp does....the throttle positioning sensor TPS has done this to me when I first installed a ported throttle body. It only happend once and it was while I was hwy driving.. same throttle position of a long period of time and when I excelled that when it hit limp mode... only did it one though.