Another update.

Today I had a chance to drive the 1998 Cherokee. I put about 40 highway miles on it and it ran fine. No check engine lights and the live data looked good.
this was with the used throttle body and sensors.

Tomorrow the new Mopar tps should come in. When it does I will install it on the original throttle body and change them back out and see if that works as expected.

noah911, I checked the voltage at the signal wire with the plug disconnected. It still showed 4.68 with the key on. So I was wrong last night. I think I might not have turned the key on when I checked yesterday. I was rushing around at the end of the day.

however when I backprobed the signal wire with the plug connected the 5 volts was gone. It showed about .9 volts. Then I manually opened the throttle and the voltage went up to 4 volts.

Im still confused about the 4.68 volts on the signal wire with the plug disconnected. I have to check another good running 4.0 to see how it compares.

I also checked for resistance between the signal wire and the 5 volt supply wire on the disconnected plug as Lawsoncl suggested. It was a open circuit like it should be.
So that should rule out being shorted to the supply wire.

I will see what kind of results I get when I install the new Tps on the original throttle body.

But right now it is running fine and all the live data is good.

Can anyone out here easily check their 4.0 for voltage on the signal wire with the plug disconnected and the key on for comparison?

Or I can check my other one if it’s here tomorrow.

thanks to all

Joe W

 

I cannot find it anymore what it was I read about the 5V being a normal finding like that on the signal wire when having the TPS disconnected. I kind of remember it but, kind of not. So, take it with a grain of salt, and understand why the details are small and vague...

The signal wire circuit from the TPS to the PCM is a 'floating' input circuit. With nothing providing a voltage to the input of the PCM.. without a source voltage, essentially, it could read anything. Having a reading of 0.5V is just as normal as seeing 4.99 VOLTS on it when having it disconnected. This is the way it is because by reading the signel line voltage from the plug alone like that, you are reading the input to the Analog to Digital converter.

 

Ok, that means don’t bother reading the signal wire voltage at the plug while disconnected.
Next time I’ll only pay attention to the signal wire when back probing the connector when it’s hooked up.

I definitely learned from this experience.

thanks for helping me understand this

 

I’m pretty sure I had the same issue with getting the 5v reading from the connector when unplugged. I don’t remember exactly what it was but something that would provide voltage under a certain situation. So yes it’s normal from what I found. The only reason I suggested removing those fuses is because that’s what fixed the problem I had. I was getting the same codes for TPS voltage but my jeep would actually stall if I turned the wheel all the way in one direction. I’ll dig up the thread I posted and link it here just because I think I posted what I read about the 5v being there when I didn’t think it was supposed to.