1991 Dodge Truck engine check light not wotking

The Check Engine light is run by the Engine Computer under the hood. If the fuse were blown for that circuit, other things wouldn't work. A burned-out bulb would be the most likely suspect, but if you had no voltage on the socket right after turning on the ignition switch, I'd be looking for a break in the wire between the bulb and the computer.

You can get codes with a scanner too, and they will let you view a lot of other information and command the computer to do things. For that age of vehicle you can find a lot of good deals on eBay. Do a search for a Chrysler DRB2. I have one of those, and I have a MONITOR 4000. The Monitor is almost identical, and is made by the same manufacturer, but with one cartridge it works on Chryslers, Fords, and GMs, but they never do all the things the manufacturer's scanners will do.