I have a 1986 302 f150 i am getting a obd code 63 So i checked the 3 wire tps i am getting ground, with key on engine off reference wire is getting 5.9 volts , single wires is getting 15 volts that's the part i don't get. Move the throttle stays at 15volts does not change unplug the tps from the wires still getting 15 volts on single wire. should it be getting 15 volts unplugged like that ? I dont think so. i am not sure. I don't want to go out and buy a 36$ tps if there is nothing wrong with it and the problem is some thing else.

 

From my notes I have that you want to check the voltage between the black/white wire (negative) and the green/lt. green wire (positive). The most critical measurement is at the throttle closed position, which should read as close to 1.00V as you can get. What's ironic is that the throttle position sensors they sell for these trucks aren't adjustable, yet the adjustment is very important. I've read many times that Motorcraft is the one to get, though I got by with a Borg Warner, but modified it to give me some adjustment. Once I installed it and worked at it until I got to read .99V with the throttle closed, that truck has run darn near perfect! Very responsive on the throttle, and it's tendency to drop RPMs too much when you changed from Park or Neutral to a forward or reverse gear went away.

 

You should never get over 5v on any of these circuits. Test some of the other sensors in the truck. If you are getting over 5v on these also, you might have a melted wire that is putting 12v onto the 5v line, or there is something wrong with the computer.

I think what I would do is unplug the computer, and then take a voltage reading. If you still have voltage, then you must have a melted or miss-placed 12v wire on this circuit. If you have no voltage, and then get 15v with the computer plugged back up, I am thinking there is something wrong with the computer power supply.

 

Ok i will check that out when i get off work and let you all know.