smusaf60

I can't seem to find the problem with the TPS on my 92 Cherokee.

It started sputtering and the check engine light came on. The code reader at O'Reilly's indicated code 24. According to a Chiltons manual, probably my first mistake, that indicates TPS voltage high or low. What I have done up to now is change the TPS.

Through ALOT of research, here is what I think I know... The TPS connector has 3 wires.
A purple/white wire, which is the input from the control module. With the key on but engine off, using a voltmeter should read about 5 volts DC, (Vdc). It read 4.99.
The orange/black wire, which is output from TPS to control module. Chiltons says it should read between .5 and 1.2 with the throttle closed and above 3.9 Vdc wide open. It read .8 with throttle closed and goes to 3.8 with throttle wide open.
There is a third wire on the connector at the TPS, blue/black, that Chiltons says goes to a ground.

So, I change the TPS and I was advised afterward to disconnect the battery to, for lack of a better term, reset the control module. I was also told to drive it around and after 25 miles the control module will reset. Today I drove 25 miles one way. After 30 minutes, drove 1 mile. Drove 25 miles back home. All with no problem. 10 minutes after getting home, drove 1 mile and the problem started again.

Of course, Chiltons raises more questions than provides answers. It says code 24 is TPS high or low voltage. So is it talking about the input or output voltage??? The readings I got were correct. Should I start following the wires and find a fault somewhere? Should I replace the control module?

If anyone can advise, PLEASE do. I'm disabled, on disability income and really need this car.

Radi

Start by checking that ground wire. If there's a bad ground connection the TPS output voltage will rise and throw the code. Might check all the relevant grounds- battery to engine and chassis in particular.

XJwonders

I agree, checking all grounds is the easiest and cheapest way to ensure the electronics are functioning properly.

smusaf60

The Chiltons wiring diagram shows the ground wire spliced with several other sensors and goes to the control module to be grounded. Should I just cut the ground wire and ground it directly to the engine block or frame???

XJwonders

I'm not sure about that.

Radi

I think Cruiser54 has a write up on fixing up that particular ground point.
I believe it's post #6 here:
https://www.cherokeeforum.com/f51/cr...x-tips-153657/

smusaf60

Thanks Radi,

Even tough the Renix system was not used after 1990, I'm gonna check all the grounds mentioned in that posting. Hell, I'm desperate. I'll update tomorrow. I'm disabled and not as bendy as I used to be. I got to get one of the kids to come do the work for me.

smusaf60

Well folks, I'm at a loss. I checked all the grounds and even used a quick connect to basically splice a wire into the ground wire at the connector and ground it to the chassis. An AutoZone guy told me it could be caused by the oil pressure sending unit. I'm at my wits end and my last option it seems is to have a Jeep dealer do a diagnostic. Thanks for all the input guys...it was worth a shot.

94XjSport94

I had the same problem on my 94 because the purple/ white wire had a bad spot in the harness somewhere so I spliced into it at the ECU and then back at the TPS, problem solved.

Try this with a good bit of wire to spare.

smusaf60

Was it happening intermittently? This only happens to me after I've been driving a little bit and it gets good and warmed up?

94XjSport94

Yes. Mine was whenever it wanted to

smusaf60

OK, The purple/white is the input from the ecu and SHOULD read 5 volts DC. Mine reads 4.9 volts all the time. But I'm desperate and I'm gonna try it tomorrow. I'll update then. Thanks!

94XjSport94

.1 volts won't make a difference.


It might measure fine sitting still and not moving but driving it could reveal a bad spot

Programbo

Let me tell you a story. I kept having problems with my XJ. Would run fine then after a bit the check engine light would come on and it would start running rough and it would always say TPS code 24. I tried EVERYTHING to fix it. This went on for years. Nobody could figure it out. To make a long story short it turned out the TPS and MAP sensor both have a purple and white wire coming off of them and they go into a harness and combine to become a single wire from that point on. Well it seems this connection had broken some how at the point after they joined so whenever the MAP sensor tried to send a signal to the computer it ended up going to the TPS instead and the TPS would sense this unexpected voltage coming in and think something was wrong and start adjusting the gas air mixture and you can follow what all that led to. I only figured this out after cutting all the loom apart and tracing every wire and seeing where they went. Once I cut the wires and soldered them together correctly the problem went away and has never returned.

I'm not saying this is your exact problem (I hope it is and you are fixed tomorrow) but just showing how you need to think "outside the box" for this kind of unexplainable problem.

smusaf60

Programbo, with all the input I got from you and 94XjSport94 and my son-in-law (a wrench at a Jeep dealer) I'm going to undo the harness and inspect the wiring up to the MAP and probably replace the MAP. (Son-in-laws suggestion). Those are the only two components tied to the ECU with the purple/white wire. If this don't work, the Jeep don't know it yet but it's committing suicide.