I have a 1994 v6 3L truck that has a speedometer that sometimes works but doesn't most of the time. Possible problems could be the Speedo head or the VSS, but its odd that the thing still works sometimes. I would like to know the exact problem so that i only have to make one repair. I occasionally get a check engine light after the Speedo stops working. Any way the code would tell me what the problem is? If so, how? Any suggestions would be much obliged.

 

Your VSS1 is failing. It starts by working only about 95% of the time, and slowly works its way to 0%.

They are about $300 from the dealer. RockAuto has them for $140-$190, depending on your drivetrain.

Yes, of course, the code would tell someone what the problem is. But if you don't tell us what the code IS, it's not going to be one of us.

If your question is "how do I read the code?" start over, search a tiny bit on this site. Those instructions are given about 3 times/day.