97 HELLLP PLEASE PO123 TPS

[volaredon]

1st post but not new to Jeeps or ; Working on my wife's 97 XJ "Country"; dead stock except for urethane 4-link bushings (love em)
4.0, AW4, 3.55 d30/8-1/4 231 T case, Michelin (the best!) 235/75 R 15s, daily driver no lift. 125K miles, owned nearly 2 years, since 101K miles
WARNING LONG POST; but please bear with me, I want to get as much info out as I possibly can
I did several searches and everything points to clockspring. I have that unhooked and no change I am at a loss; been fighting this garage ornament since July! 2 ECMs 2 wiring harnesses (NO a 98 one WILL NOT work regardless what the junkyard countermen say)

Back in July, I powerwashed the engine on a Sunday (diesel fired steam cleaner) Ran fine after. Fine Monday. Tuesday morning, the idle went goofy, tranny wouldn't shift, (acted like pedal was floored) and all of a sudden gas gauge moves faster than the 440 in my Mom's '73 Plymouth wagon did; very unlike this XJ! has been parked since.
PO123, PO700, (dont remember number on this one "TPS does not agree with MAP";

Problem is, I am getting 4.69V at TPS with TPS UNHOOKED and 4.92V by plugging it in. key on engine off, scanner says 87% gas pedal application whether the pedal is touched or not.
so being that I am getting those readings unhooked I can eliminate TPS as the cause.
With the #1 connector unhooked from ECM I have 6.XX on orange wire at TPS, which should get its 5VREF from the computer; being unhooked it should be dead. I do not understand this.

I have a factory service manual; I hate how it's laid out, too much page flippage compared to the older ones, and not even any fuse box diagrams!!!
I first suspected Splice S114 where the grounds for 5 sensors come together about even with #2 injector; I went to check that splice and the wiring was a melted glob that peeled apart like Twizzlers candy; and the wild goose chase started; dealer buddy said harness had to come from a 97 only; I went junkyard hopping, most said they cut all harnesses and dont sell them; I walked by many 98s figuring "won't work";
--Finally found a 97 in a yard and got the engine part of the harness and plugged in; no change.
--Cleaned every ground "shiney"; no change.
--Plugged in known good TPS; same result;
--Bought new Crank sensor, plugged it in/alligator clipped it in for ground and same result; so I returned;
--Got another ECM; now it idles correctly but still same TPS issue;
-- Replaced the entire engine compartment wiring harness from a 98; started, ran but every plug having to do with tranny was different; but TPS issue still there.
--finally found a 97 whole engine compartment wiring harness after too many wild goose chases and tanks of gas spent running around; plugged it in; came from a early production "Sport" with crank windows and no foglights, differences noted but only had to do with accessories; not essential engine function; NO CHANGE! SQUARE ONE.

Oh one more thing; When I got this Jeep, it had an aftermarket remote start that had a mind of its own on it, would randomly start up without being "commanded" to; I removed this totally, and repaired all wires tied into by remote start system.
CLOCKSPRING IS UNHOOKED TOTALLY and same result;
I am so tired of this garage ornament and am ready to push it out poke the gas tank and toss a match under it; this is not my 1st Jeep, but the most frustrating one. I am fed up, on Disability, in College full time, and cannot afford to pay prevailing wages for someone else to take a stab; nor can I replace the vehicle. My wife is on me hard as winter approaches and she grows ever tired of driving a stick shifted TJ.... (I miss the TJ as much as she hates it)

 

[volaredon]

oh one more thing; the computer swap did give me some different results; the orig one when 1st scanned gave me a laundry list of 2 digit and 3 digit codes the 1st time I scanned it; I mean really weird; like "65; something about a diesel water seperator" that we all know the 4.0 is a gas engine not diesel; see what I mean about off the wall? these codes have never shown back up. Also with the orig ECM, (still have and have swapped back n forth a few times)
The orig ECM will not let it idle below ~1250 RPM and is more erratic and "jumpy"--never was prior to this issue.

the 1st replacement ECM was from a 96; engine ran, no gauge operation, but agreed on PO123 and the actual voltage shown via scanner. I gave that ECM away to someone I know, that owns a 96 model.

the 2nd ECM, a junkyard refugee from another 97, (in my Jeep now) lets the engine idle smoothly at what the scanner says "target RPM" but still cannot get rid of PO123 long enough to release the button on the scanner upon resetting codes; voltages via scanner regarding TPS are identical to other 2 ECMs.

How can I have voltage on the orange line with teh ECM unhooked? Same result with replacement harness; 6.XX volts on orange wire at TPS via Fluke meter as was on original harness.

PLEASE HELP ME; I am beyond flustered! former 18 yr ASE Certified tech, to boot.

 

[whitexj98]

Have you followed the trouble shooting steps in the FSM for P0123?

 

[larsen]

Take readings with the TPS connected by back-probing the connector. If the scanner says the throttle opening is always 87%, no matter where the pedal is, I'd suspect the TPS or wiring is bad. The ECM probably switches the path to ground for the orange wire.

 

[volaredon]

how can teh TPS be bad when I get the same reading with it DISCONNECTED???
I tried another one for the He11 of it and no change.
and the fact I have almost 7V on the 5VREF signal wire with the connector that is supposed to feed it unhooked from the computer!

 

[Tim_MN]

You seem to be focused too much on the symptoms and not on the cause. All the 5-volt sensors are on the CCD Bus circuit and any that are faulty or shorted can put 5-volts where it shouldn't be. If having 5-volts on the orange wire is not right (not yet proven) it has to be getting there somehow from another sensor or sensor wire harness.

TPS from Advance/IdiotZone/O'Reilly have been proven to be out of specification or failed right out of the box. Are you using a genuine JEEP TPS ?

Also, water and the TPS do not play well together. If the TPS has been wet and you experience TPS or AW-4 issues, suspect that the TPS has gone bad.

P0123 Possible causes:
- Throttle position sensor harness is open or shorted
- Throttle position sensor circuit poor electrical connection
- Faulty throttle position sensor (Tested yet ?)
- Faulty Powertrian Control Module (PCM)

The P0123 code will set if the monitored TPS volts rise above 4.94 volts for the peroid of 0.48 seconds.

 

[volaredon]

no I didnt buy a new TPS; I put one on there from another TB I had sitting around from a known good running vehicle.

what I don't get, is that the 5 VREF is either terminal #17 or terminal #23 (I forget which I can look it up in the FSM) at the ECM plug; that 5VREF is supposed to be fed from the ECM at that terminal; so with the #1 ECM plug unhooked, the orange wire anywhere in that "loop" should be DEAD; so then why do I have 6.something volts, on a line that is supposed to be dead?
I have the dash apart the clockspring unhooked, (for what seems like the 20th time) because everything I see related to these symptoms points that way;
--on a correctly running vehicle what should I have at that orange wire with the #1 ECM plug disconnected, under key on engine off condition?
--Under same conditions, and everything plugged in erxcept the TPS what voltage should I see?
I also have voltage on the "return" line, that should not be there unless connected to the TPS which should be a "modifierd portion" of that 5VREF.
The way I understand it the orange feeds the sensors the 5V, the TPS acts as a rheostat (like a dimmer switch) and sends a portion of that 5V back to the ECM.
Both wires should not have juice on them especially when unhooked from both the TPS AND The ECM. but they do.

 

[volaredon]

If go to the stealership and buy a genuine Jeep TPS, will outside voltage on this line, "fry" the new TPS? I have another known good used OEM one around here somewhere; I think it may in my other toolbox, which is in the back of my son's truck....

 

[volaredon]

oops double post

 

[Tim_MN]

1999 TPS unplugged, Key to ON/Run, engine off:
Black - Ground OK - 0 volts
Orange/Black stripe- 4.3 volts
Orange - 5.1 volts

 

[volaredon]

so the black/orange and the orange are supposed to both have juice on them?
I had juice on my grond one as well/ my mind is on knots with this thing.

one thing I am gonna do, is to re install my orig underhood wire harness since the one I found in the JY was a "less loaded" one, and TPS wise all my results are identical to with the orig harness.

I will have both a 97 and a 98 XJ underhood harness for sale and soon.

 

[Outlander560]

sounds like you have a grounding issue...it is internally grounded into the pcm. it as well shares the same ground with the IAT and the ECT which can infact be your whole problem.

back pin the ground wires on your IAT and ECT if the IAT and ECT ground are good then the wire is internally grounded correctly at the pcm,(so you dont have to go through that mess of wires) if not then your going to have to check for your ground at the pcm

NOW if the wires are grounded at the IAT and ECT your are going to need to open up the harness and locate the S114 connector inside the harness
OR
you can cut ground and make a new one since opening up a harness and locating a wire is no easy task thats if it is the issue

to answer your latest response
Orange wire is your 5v ref
orange/black is your signal so at idle you should be reading 0 volts

 

[Outlander560]

now what leads me to think a short in the signal wire could be the case is because the Transmission Module is spliced into the TPS signal wire going into the pcm. so you might have a few issue in the harness....

But wiring is tricky solve the ground problem first then move to the signal. dont throw a tps at just yet until you know for sure that the wiring is good

 

[volaredon]

I have changed engine compartment harnesses TWICE so you think that I have had 3 bad harnesses? and the immediate engine harness once.
and I went to great lengths to shine up every single ground connection.... more than once.
I know where S114 is, because that was my 1st wild goose chase, resulting in finding a melted together blob of wiring on the engine wire harness (the one that goes along the intake and goes to the injectors and sensors) and led to me changing out that engine harness.
Would it be OK to splice into one of the wires on one side of that S114 and put an eyelet on it, then run it to a known good ground or would that screw with the computer?
I could buy a new CTS, plus a new CPS, CKP, TPS MAP and IAC and still have this issue! I wouldn't mind replacing a few of them but definitely not all of them, especially knowing that after spending that much, I could still be at Square One!

 

[volaredon]

I do apprecate the replies, I am just trying to sort all this crap out in my mind, it's still in knots!

At one point I disconnected the Crank, dist p/u, the TPS the Trans module under the dash, and the MAP and if I connected EITHER the crank the TPS the MAP OR the trans control box one at a time, the TPS voltage would go from 4.64 to 4.9V with key on/engine off, only the coolant temp sensor and the dist pickup did not have this effect. I have not tried this since putting the latest engine compartment harness on.

I have disconnected everything that can be and still have a scanner reading for the TPS, both individually and "all at once" while the orig wiring harness was still there and my TPS voltage stays the same. a reading with a FLUKE meter at the TPS confirms these readings.

 

[larsen]

97 XJ ...4.0, AW4 ...
... powerwashed ... idle went goofy, tranny wouldn't shift, (acted like pedal was floored) and all of a sudden gas gauge moves faster ...
PO123, PO700, (dont remember number on this one "TPS does not agree with MAP";

Problem is,... scanner says 87% gas pedal application whether the pedal is touched or not.
...

If this is true, there's no TPS feedback signal corresponding to the throttle opening. Like the TPS is "stuck" or not attached/linked properly to the throttle body, or defective.

 

[volaredon]

If this is true, there's no TPS feedback signal corresponding to the throttle opening. Like the TPS is "stuck" or not attached/linked properly to the throttle body, or defective.

the weird part is that I get this reading whether the TPS is connected or not. the only difference there is that disconnected I et a TPS reading of 4.67V; connected I get 4.94; it varies as I touch the gas (goes higher yet) but extremely little. what has me in circles is how the He11 can I have 4.67 volts from a sensor that is unplugged?
and how can I have any juice on that orange with the plug on the ECM taht is supposed to feed that wire in the 1st place, also disconnected? (again this verified by a Fluke meter)

 

[whitexj98]

Well trace the wire back, it must be shorted somewhere but like I said eariler, have you folowed the checks they list out in the FSM for P0123?

 

[Outlander560]

wow 2 engines harness's i did not realize that. What about the pcm itself? the pcm could have been fried do to the short from somewhere in replacing a shitty engine harness. cuz as im sure your well aware of once that signal gets a volatage of greater then 6v it could potentially cause an issue with the internals on the PCM...if all of this is true i would have suspected a faulty PCM if i do recall i know you replaced a PCM however did you change the harness with a different one and then change the PCM I dont know what scenario you did first

 

[volaredon]

I have had 3 PCMs on this thing as well.
I still have 2 of them; the original which adds "no idle below 1250" to the mix, the other one I have it does idle as it should but all scanner data not related to idle RPMs agrees between them.
Replacing the PCM was my 2nd move way back, the 1st being to remove the remote start setup that was on there when I bought the Jeep.
the remote start had a mind of its own, starting out of the blue at will without pushing the button; I could put the keys in the cupboard to be sure the cats werent accidentally stepping on the fob during the night; and during the day my wife had the keys in her purse in a locker halfway across the store but it would erratically start when it felt like it; sometimes multiple times daily sometimes a couple weeks between;
she often had co workers and customers taht know her come in the store and ask why she lefy her Jeep runnin while she was inside working with several hours before quittin time. so I eliminated the remote start and made sure it was out of my misery with help from a sledgehammer on the driveway.