Chevrolet: computer codes, gmc van, gm vehicles

Question
I have a 1990 gmc van 4.3 i think (chev van) on the older cars you used to be able to stick a spade in the slot and get the number of times the light flashed the get the code. Is that still possable and if it is where do you get the codes?
Bill

Answer
Yes, you can jump across terminals A & B to get the codes to flash. This works on all GM vehicles upto 1994. After that you have to use a scan tool.
You can let me know what codes you have or you can get a manual that should have the diagnostic flow charts needed to test the different systems for whatever code you have. You can use Chiltons or Motors manuals and you can probably find them at the library or a book store.