Mr. 5.0 and mustangII460, both made excellent posts....but....
WTF is this "TEST WIRE" you keep referring to??? There is no such thing as a "test wire." Do you mean the
+5VDC, ground, or signal return??? The black wire should be GROUNDED through the harness, at the computer's chassis, then to vehicle (and battery) ground.
Take some pictures or something; you're confusing the heck outta me, dude.
You should be reading voltage like this:
1. Connect the NEGATIVE lead of the DVOM to the NEGATIVE terminal of the battery.
2. Make sure the DVOM is set to read "Volts," automatic scaling if possible.
3. Turn the ignition switch ON (engine running position but without the engine running).
4. Leave the TPS connected!
5. Using a hat pin, pierce the wire insulation far enough so the pin is almost sticking through the other side of the insulation, one wire at a time; do it on an angle of about 30 degrees from the wire's axis, so you save your fingers.
6. Connect the POSITIVE lead of the DVOM to the hat pin.
7. RECORD the voltage you see on the DVOM.
8. FOR THE LOVE OF GOD, record the
color of the wire with the corresponding voltage.
Present your findings here, and I'll be glad to help more.