My 2000 F250 diesel has apprx 215k miles will just cut out at highway cruise like someone rapidly turning the key off and on. Also, when at idle, it may just die. Either at a stop or when coasting down the driveway. Seems worse when the engine has not warmed up yet. This has happened several times, but only when the weather is rainy or really foggy-lots of moisture in the air. The other day, when this happened a couple of times on the highway, the service engine lite came on, but disappears at the next startup. (has done that before). Oil and filters are good. I suspect something electrical, because of moisture, but what. Local mechanic could not get any readout on his diagnostic, wants to spend some time checking fuses. Have not taken to the Ford dealer yet. Any ideas? Thanks.