Well, the truck (03 1500 Q/C 4.7L 8ft Bd) is back from the dealer, recall the MIL acitavated for the fourth time since purchase last 03. This time the service manager handled the transaction and did a great job. The diagnosis: faulty natural vacuum leak detector pump. He replaced the part. Time will tell if this measure corrected the origninal fault - the last couple of MIL activations occured when we had rain for a few days straight and the fuel level was near 1/4 tank. Haven't had those conditions since the truck was repaired. Anyway, again thanks to all for the information provided a few weeks ago. I think it helped.

Jim