I was doing a pioneer CD/DVD/Nav unit in an 08 tiburon. The radio install was normal and all I needed was a vss wire and reverse wire.
I found the reverse wire in the harness in the drivers kick (gray)
I used my audiovox tech site and they said the speed sensor wire was (brown) in the obd2 plug under the dash. I jacked the front of the car and used my multimeter to test the wire. I showed 12v DC on ignition and when I switched to AC it was 0.00v in neutral and .128v in first gear and voltage climbed up with engin speed. What I did notice is that the spedo wasnt working right off the bat.
I have checked all fuses and the electronic speed sensor on the manual treansmission. I have put it on a scan tool with no luch and also disconnected the battery
The only wireI touched (the brown) is still reading 12v.
Im totally clueless at this point

I'm not fimiliar with the hyundai electrical system but this doesnt make too much sense. The car does have an intake on it and has around 1500 miles on it

 

you need a speed "pulse" not a constant voltage.... you should go to the back of the speedometer and remove the two connectors that look the same in size. when looking at the connectors unplugged on the female sides. The top (with the pinch latch) second pin on the right-most side, should have a blue wire coming out of the back of it. This should be your speed pulse wire. Try tapping into this and see how that works.