The state inspection computer wont read RPM on my 2002 Taho
 

Passed inspection and when the tech hooks up the computer to read for the State , no rpm is detected. The fuse is good .just wont recognize the truck .

I'm a home mechanic and you should confirm the following, but there are speed sensors on the engine and trans that send info to the computer. But a faulty speed sensor should result in a check engine light coming on. Another guess is that your speedometer cluster may be faulty, and rpm is not being sent to the OBD port. I have an '01 Suburban with 235K and have had a fair share of problems, but not like yours, so my only experience is what I have read on the subject. I make my own repairs when I can, but anything in the dash is off limits in my garage. Hopefully this info narrows it down for you.

And a possibility,the glitch is on their end,to rule that out,hook up a reader at a parts store,ask them to scroll down to rpm