Flashing chech engine light means you have a potentially catalyst damaging misfire.

DO NOT DRIVE THE TRUCK LIKE THIS!!!

I'm not saying you should be afraid to drive the truck to the shop to get it fixed, but trust me, you don't want to screw around when that light is flashing. Cat converters are very expensive.

It's not an O2 sesnor or something like a gas cap left off. This is a serious misfire being picked up my the computer.

Things to check in your own driveway: spark plug wires and boots, spart plugs, dead cat caught up in the belt, that sort of thing. If you have a distributor, there may be water in it or for DIS, perhaps a grounded plug wire pringing down two cylinders.

Clay