I had this issue. I would start the truck, it would run fine for a while and then all of a sudden the lightning bolt would start flashing and the truck would go into limp mode. I tried checking connectors, replacing the accelerator pedel, cleaning the throttle body, nothing worked. I tried to pin down the conditions that made it happen and thought it was mostly when the weather was hot, and would happen every 3rd time I started the truck.
It eventually got worse to the point where it was dangerous to drive, so I brought it to the dealer. They first replaced the PCM under warrenty, that didn't solve the problem, so I brought it back...turns out there was a faulty wire in the wiring harness (I believe leading from the accelerator pedel to the PCM). They replaced the wire and it was as good as new. cost me about $700 though
I would say you really need to have a dealer look at this and do thier diagnostics. Otherwise you are just taking a shot in the dark, like I was.