Thor, welcome to TDP.
You can pull your own codes on a 94. You need a paper clip or short peice of wire bent in a u shape. Under the steering colum is a plug receptical and you want to connect the two top right pins in the connector. Now turn on your ignition switch and count the flashes of the Sevice Engine light. 1, 1,2, 1, 1,2 1, 1,2 says everything is good and working. Any other combinations will flash 3 times then on to the next. Write these down and let us know what you read. And don't forget to remove the jumper when your done.
"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
-Patrick Henry
A5150nut
2006 K3500 D/A
94 6.5 4x4 5spd Sold