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another "non-TPS" TPS issue

D

DJTimyD

NAXJA Forum User
Location
Colorado
So I am tired of throwing parts at this, but I am also tired of it not being fixed.

2000 XJ Sport 4.0L 4x4 AW4 NP231 D35 front Cry 8.25 rear

ISSUE: 0122 code (TPS low voltage)

PRESENTATION: low and rough idle, dies after release of throttle, RPMs drop out rather than stagger down when throttle is released, CEL, TPS shows 0% or 100% in Torque App

STEPS TAKEN:

1) Checked connections to both IAC and TPS. Cleaned and reseated both connections. Reseated the connectors to the PCM, and reseated the PCM itself to ensure proper grounding - no change

2) Replaced IAC (it was dirty, had been cleaned once before by me years ago, and the spring action was janky - should be able to get another 200k from this one) - rough idle gone, low idle and CEL persists

3) Replaced TPS - no change

4) Tested new and old TPS using a safety pin on the back of the connector - Voltage is correct on source, variable voltage within tolerance with no spikes or drops, ground connection good, tested while taping on connector and while wiggling the cables, no changes in test results.

5) Pulled horn relay (W.A.G. from reading another kinda related post) - CEL off and idle upto 650-700, Torque shows TPS at ~15% at idle

** 0122 code shows as pending in Torque, but the CEL does not light at this point **

6) Replaced clock spring with NEW part (old one was scrounged from junk yard) - no change.

NEXT STEPS:

This is where I am stumped. I could entertain the possibility of there being a wiring issue, except for the successful tests of the TPS. I could entertain the possibility of the computer being the issue, except that its just this one code, and reseating the computer and the connectors had no change.

I am perplexed as to what could be the issue here. At least the rough and low idle have been resolved, but when its time for this to go for emissions tests, I wont pass because of the stored code. Also, I'm hesitant to take it on trails because if something changes, I could be stuck, whereas if I am in town, I can make a phone call.

Any ideas and suggestions are welcome. I'll entertain just about anything short of burning it to the ground or hitting it with my purse!

Thanks!
 
Last edited:
DJTimyD said:
So I am tired of throwing parts at this, but I am also tired of it not being fixed.

2000 XJ Sport 4.0L 4x4 AW4 NP231 D35 front Cry 8.25 rear

ISSUE: 0122 code (TPS low voltage)

PRESENTATION: low and rough idle, dies after release of throttle, RPMs drop out rather than stagger down when throttle is released, CEL, TPS shows 0% or 100% in Torque App

STEPS TAKEN:

1) Checked connections to both IAC and TPS. Cleaned and reseated both connections. Reseated the connectors to the PCM, and reseated the PCM itself to ensure proper grounding - no change

2) Replaced IAC (it was dirty, had been cleaned once before by me years ago, and the spring action was janky - should be able to get another 200k from this one) - rough idle gone, low idle and CEL persists

3) Replaced TPS - no change

4) Tested new and old TPS using a safety pin on the back of the connector - Voltage is correct on source, variable voltage within tolerance with no spikes or drops, ground connection good, tested while taping on connector and while wiggling the cables, no changes in test results.

5) Pulled horn relay (W.A.G. from reading another kinda related post) - CEL off and idle upto 650-700, Torque shows TPS at ~15% at idle

** 0122 code shows as pending in Torque, but the CEL does not light at this point **

6) Replaced clock spring with NEW part (old one was scrounged from junk yard) - no change.

NEXT STEPS:

This is where I am stumped. I could entertain the possibility of there being a wiring issue, except for the successful tests of the TPS. I could entertain the possibility of the computer being the issue, except that its just this one code, and reseating the computer and the connectors had no change.

I am perplexed as to what could be the issue here. At least the rough and low idle have been resolved, but when its time for this to go for emissions tests, I wont pass because of the stored code. Also, I'm hesitant to take it on trails because if something changes, I could be stuck, whereas if I am in town, I can make a phone call.

Any ideas and suggestions are welcome. I'll entertain just about anything short of burning it to the ground or hitting it with my purse!

Thanks!
Click to expand...

What's the TPS voltage at idle? Is there a throttle stop that needs adjusted? I vaguely recall the minimum voltage at idle had to be .45 or .6 volts.
 
Genuine Jeep TPS ? TPS min and max voltage observed ? The spec I find is .25 volts at minimum throttle opening (idle), and 4.8 volts at WOT wide open throttle.

There should be no reason to adjust the butterfly plate stop.

Failed wire splices and/or chafed wire insulation in the wire harness are possible also.
 
Did you check the TPS for "fitment", when I bought a new TB it bound up with the TPS shaft, not working "freely".
 
I cannot remember the values at this point, however I looked at several guides/how-to's for the voltages and BOTH the original and the replacement TPS registered the same values (+/- .05 volts) and both within the specs posted. Even if the replacement NAPA part is not a Mopar part, it was generating the same results. I returned the NAPA part since it was giving me no benefit (change part = no change in issue) and I'm using the original. I can retest to get the exact voltage... if y'all really think its necessary with the updated information.
 
Here is my thread, just about a year ago: http://www.naxja.org/forum/showthread.php?t=1137127

I chased the TPS gremlin for weeks -- 2000 XJ -- Read the thread if you want my details

My problem was not with the TPS although 0122 was always present -- The problem was a stuck exhaust valve -- The stuck valve was dumping raw fuel into the exhaust, the O2 sensors where interpreting that fuel as open throttle and throwing the 012 code


My suggestion -- don't do anything else till you do a compression test

The only other visible symptom I had was a glowing exhaust pipe below the precat for 1,2,&3 cylinders -- obviously the extra fuel burning off

I can't stress enough to do a compression test...
 
Thanks for the tip. I never would have thought of that. I'm gonna run down to harbor freight tomorrow and buy a tester. Although I don't have the red hot exhausted manifold or the gas mysteriously disappearing, and have resolved the rough low idle at temp with a new IAC, I will try just about anything. I'll post results tomorrow.
 
Compression checks out:

khohhd.jpg

The lowest

7qHE1Q.jpg

The Highest

I used a rent-a-tool from AutoZone so I'm not sure about the actual reading, but I was concerned with large discrepancies between cylinders and there are none.

As a side note - the Harbor Freight set sucks - don't buy it. Also Advance Auto Parts wont loan out the Compression Testing tools. Talk all the smack you want about AutoZone, but they came thru for me today.

I'm very happy that was not the issue. I had been wanting to test for a while because I have a 2000 - and everyone knows about the cracks in the head issue. While I cant say 100% that I don't, the lack of coolant in my oil, coolant out the tail pipe, and good compression give me a little bit more security about my head. Too bad that isn't the gremlin I'm chasing right now...

So regarding this gremlin, I do not have a stuck valve dumping gas down my exhaust and messing with my O2 sensors, which could in turn mess with my TPS because of the shared ground. It was a long shot to begin with - but its for all intents-and-purposes eliminated.

I am open to any more ideas - no matter how far fetched or odd ball they might be. Anything to save me from redoing my wiring harness would be welcome!
 
Last edited:
Forgot to mention above - and I missed the "edit window" for the post - ugh...

I changed the spark plugs out. They were not bad, but not good. They were defiantly not new, but they were dry and they were close to the original gap with no scarring - and I figured while I was there, why not. Used Champion Coppers, which is what came out of it.
 
The IAC can get out of sync if the ASD relay is malfunctioning.
 
old_man said:
The IAC can get out of sync if the ASD relay is malfunctioning.
Click to expand...

I had not thought of that, mainly because its not cutting off and all of my performance issue were resolved by replacing the IAC and then later removing the horn relay. For ~$10 I can try that - but my concern would be not so much the relay, but the wires going to it, and also the wires that go to other sensors (O2 for example) that may be the culprit but then in turn cause the ASD to trigger. Which leads me back to an electrical gremlin... ugh

I'll buy one (cant hurt to have a spare and its pretty universal from what I can tell under the hood) and try that. Throwing $10 at this isn't like throwing $200 with no result...

Also - greetings fellow Lovelander!
 
Why are you suspecting the wiring harness? OHM out the wires -- shouldn't be to hard to find the pin out for the ECM to check -- If you read thru my thread I bet I wrote down the pins at ECM for the TPS
 
Heavyopp said:
Why are you suspecting the wiring harness? OHM out the wires -- shouldn't be to hard to find the pin out for the ECM to check -- If you read thru my thread I bet I wrote down the pins at ECM for the TPS
Click to expand...

I assume you mean the PCM... and I have already tested the leads going into the TPS, as stated in my first post. I suppose I could check the wires that come out of the PCM, rather than going into the TPS, but since I was not able to find any issues with the values at the wires going into the TPS, I'm just not sure what that would get me.

Unless you are suggesting checking the values of all the sensors that share the ground with the TPS at the PCM, which I suppose I could also do. Short of reading thru all the FSM wiring diagrams , do you know where I might find the correct input and output readings for all the sensors? I would also need all of the resistor values for any resistive device connected to that shared ground as well - i.e. cruise controls.

But doesn't this process, of checking values at the PCM, just lead me to the same possibility as before -that there may be a fault in one of those wires somewhere in the wiring harness that will cause this code?

I guess that is how I came to suspect the wiring harness MIGHT be a possibility. I am still open to any and all, even possibly crazy suggestions ... including those requesting me to run a compression check for a low voltage code on a TPS.
 
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I was thinking to test just the wires -- If you knew the pinout you could check resistance at the wiring harness at whichever sensor and at the PCM connector -- Just to rule out a short in the actual wiring harness itself
 
That's a good idea - except for the shared ground between sensors. I could test the load wires, but if its an intermittent ground, it could be any number of wires coming out of the PCM and running from the front of the engine bay to the steering wheel.

I'll get to work on checking the load and signal wires first, since those are much more easily traceable than the shared grounds.
 
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