TPS keeps failing


New Member
Chasing down what seems like a gremlin in my WE4. My TPS keeps going failing on me. At this point, I've replaced it 3 times in 2 years. Even put a new Casper's plug on it when I found that the previous owner had wired the black to blue. My IAC is set around 35 and whenever I put a new TPS on, it stays at .42 with WOT around 4.5 and the car runs good for awhile. Then eventually it stops starting on first crank and the other day when I was on the highway it threw the CEL with my scanmaster G reading TPS too high and engine-braked until I got off on the next exit. I was able to get back going for a few days by adjusting the TPS but then it went back out of range while I was driving it.

I'm not really sure where to go from here though. Should I pull the throttle body and try cleaning it? Replace the IAC valve? What am I missing?


Brutal 6 Racing
The TPS shouldn't go out of range like you describe. I begin to wonder if your battery voltage is changing dramatically when driving. The only thing that I could envision that would cause this is if you had some kind of volt booster which is flakey. I have seen this in the past with the ones Red Armstrong used to sell if they got wet.



Well-Known Member
are you taping into the TPS for 5 volts for something else ?
I like my IAC at 20-25 but 35 is in range. just at bit more throttle blade open, but not on the screw to hard to get .42.
is the throttle body shaft in good shape , shaft tight not wobbly?


Staff member
And if your car has T-Tops, you could have a leak that is letting water drip down directly onto the top of your ECM, causing corrosion to the ECM pins and inside the wiring harness connector. I had that happened on a friends t-top car back in the day. The corrosion was only discovered when we pulled the ECM and took a good look at the pins and wiring harness connector. It was so bad that it broke one of the pins off the ECM and was stuck in the harness connector. He was having a very similar sporadic and impossible to duplicate issue like this. Cleaned the harness, removed the broken pin, replaced the ECM, swapped the chip and fixed.

I tell everyone to always keep an eye on the condition of the ECM, especially if you have wet carpet in the footwell, or behind the passenger seat. It's not impossible for a leaking heater core to leak coolant down on the ECM either, but more uncommon, due to the location of the heater core.
Check into it.



Daily Driver
The TPS has it's own "return" signal on D12 at the ECM, yeah it's a ground but only for the 5V supply.
Check all 3 wires for good continuity with an Ohm meter connectors unplugged both ends while wiggling the harnesses at both ends as far back as you can.
There's also a splice in that ground/return signal called S666 in the harness around the front of the valve cover that might be an issue causing voltage fluctuations intermittently.


Cat&wife post starter
When I was having TPS issues (not exactly like yours) turn ignition on put Scanmaster on TPS and start moving the ECM and wiring. ANY fluctuation and your ECM or connectors are suspect. Mine was the connector. To be honest it didn't look bad but it was.
Checking grounds is also another good idea.

Or you could fly SalvageV6 to you. He knows his shizznizzer.


New Member
Clean the 5 volt reference wire at the Ecm a paper clip will release it. Wrong voltage in wrong voltage out.
Which one is this? I finally had time to do some testing and I'm getting 5v when connected to the black and gray wires but when I switch to the sending wires of blue and black I get 0v. Even when opening up the throttle I still read 0v.
Sorry but electrical is not my strong suit.


Daily Driver
Where are you reading the voltage? At the ECM or Sensor wiring?
You need to provide details of how you measure things with electrical problems it's very important.
Are you still getting codes what are they?


New Member
Reading at the sensor. I'm not sure how to read on the ecm.
Scanmaster g is still reading .42 / 4.5 wot with no error at the moment.


Daily Driver
If the scanmaster G is recording normal values you posted above and there's no codes it's not an issue at this time.
I assume your 0 volt measurement at the sensor was inaccurate, you need to probe the wires with the sensor in place, key on, and that isn't easy unless you have a good insulation piercing meter probe.
If the G is reading correctly and there's no codes you may have to wait for it to happen again or do the probe test, (your meter should match the scanmaster G reading), while moving the harness as much as possible to check for an intermittent connection.