1991 Plymouth Voyager Location of plug to check gages

Computer problem
1991 Plymouth Voyager 6 cyl Automatic 200000 miles

I have a 1991 Plymouth Voyager with a 3.3 l engine. I put in a new water pump and changed the oil yesterday. In driving to work, the "check gages" light came on and the car died. I could get it to restart but only for a few seconds before it would die again. Any idea what could be wrong? I also need to know where to find the plug that I can short to get the engine codes? I could not see it under the dash or in the engine but maybe I don't know what I am looking for. All I could find under the dash is a blue plug with external pins rather than a rectangular plug with internal sockets that I am familiar with.