For the past year I’ve had issues with my TPS going bad. I have a 1998 Jeep XJ, 4.0, the problem is my signal wire has 4.5-5 volts even when the connector is unplugged from TPS. I’ve replaced everything people has mentioned that could be the problem. I’ve narrowed it down to the voltage is coming “From” the ECM and not the TPS. I’m on my second ECM and still having the same issue of voltage is coming fro ECM. Help!!

 

You're correct. The 5.0v supply comes from the ECM and it provides 5v power to more than just the TPS. When you disconnect the TPS plug and measure voltage in the connector pins then you should measure ~5v at pin 3 with reference to the ECM's TPS ground wire, or pin 1, and 5v or less on the sense wire, pin 2. When the TPS is connected, if you can insert probes (paper clips, don't let them short out) in the backside of the TPS connector at the sense wire and at the ground wire, then you may monitor TPS sense voltage w/ref to the TPS ground, and as you probably know, moving the throttle should cause corresponding movement of the sense voltage over the range of the TPS (probably ~1.5v to ~4.5v).

If your body/chassis/block grounds are rusty and ground straps are corroded/missing then it's time to do some clean-up. Without good grounds, voltage measurements may be unreliable and sensor performance unpredictable. Also note that there are splices in the harness for both the 5v supply wire and the sensor ground wire. If the sensor ground wire is intermittent then it can lead to your kind of troubles and expensive misdiagnoses. To check sensor ground wire simply monitor wire continuity with your ohmmeter from one end to the other while flexing/wiggling the harness.