Rezonance

Hey guys, I've been suspecting I have a bad tps for a while. Went out to check the voltage and it reads right about 1 volt closed, and when you open it it doesn't drop off or anything. But, when it's at WOT it has a reading of 7.5 volts. I believe it's only supposed to be around 5 volts or so. I've noticed some very low rpms when driving. The jeep never gets past about 2500 rpms, and if it does you have to punch it hard - especially going up hills. Tranny fluid and filter were done around 15,000-20,000 miles ago and full tune-up around 5,000 miles ago. Do theses symptoms sound like a bad tps? I just don't wanna throw parts at it.

dave1123

Sounds like it to me, but then again, I'm on the other side of the country. It's a good place to start because the volt readings aren't right.

Mudtallica

Only replyin' to this post due to your "voltage" issue.. I'm fixing to change my CPS, for the 3rd time in 2 months, on my '98 GC.. Surely I'm not gettin' junk sensors.. 1st one I changed lasted about 5 weeks, then it went out last week.. Put the 2nd one in this past Sat.. then the wife got in it this mornin', won't start.. Same symptoms.. IS it possible that a bad TPS would let too much voltage get through to the CPS? Or, what would cause enough of a "spike" in voltage to blow a sensor?? As with the TPS, the CPS is only suppose to get 5V..

dave1123

According to my research, the sensors should be getting 5.0 V max. This is the PCM supply voltage. If the PCM is delivering more than 5.0 Volts, it's a PCM default. I'm thinking if the PCM voltage regulator is supplying too many volts, this could be the reason the sensors don't last long.

You can test supply voltage to both the TPS and CPS. Both should be getting 5.0 volts. The TPS should be showing 0.8 volts output at idle and 4.5 at WOT. The only way to test the output of the CPS is with an LED pulse light with the engine running. I've been told you can wave a magnet in front of a CPS in your hand, and see if it reacts. I haven't tried that.

Bustedback

I suspect the PCM.

Creature85

Here's a write up on testing the CPS if you need it.

https://www.cherokeeforum.com/f51/testing-cps-5563/

Rezonance

Well, I went ahead and checked some other components before I bought a replacement TPS. Looks like the TPS, CPS, IAC, MAP, etc. are all getting over 5 volts. Looks like at least 10 or more. Looks like it might be the PCM. At 200k it's bound to happen sometime, eh? I suppose I can clean the connections, try the tie wrap trick or loosen the torx screws. Anything else that might help?

dave1123

Replacing it?

Creature85

If every other sensor is getting that big of a voltage increase then it's something on the power circuit that's going bad.I'd say if you knew anything about electronics you could repair the turn down circuit on the PCM easily enough, but if you don't then just replace the PCM all together.

Rezonance

If it was just my decision, most likely. But, money is tight and my wife is one of those people that has the mentality that if the car still gets you there it's fine - even if it has issues. So, dropping $200-250 into my car is not something that she would think is a priority. So, I'm trying to just get it by right now. At least till we have some extra funds coming our way.

dave1123

I'm going to tell you a little about "the wife"! I told my wife I needed a new starter for my truck and she told me to get a junkyard one because we didn't have the cash for a new one. About a week later, her A/C compressor went and she somehow found the cash for that! Amazing, ain't it?

Maybe you should get a junkyard one! OR, maybe you have an electronics guru friend who could fix yours.

Creature85

Sorry to hear. Only thing I could suggest is to try to find one at a junk yard.

Rezonance

Probably looking at doing that if nothing else works.

dave1123

I'm not sure on this, but you may have to have another PCM "flashed" or reprogramed by the dealer.

Rezonance

I've been looking around and it probably will need to be flashed. Needs the VIN, mileage and I'll have to find one that was programmed with a factory alarm. I'm just wondering if I got one from a junkyard would I need to go to a Chrysler dealership or could any garage do it with the proper tools and information?