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2003 jeep tj 4L ... 5V reference

  • Jerry McGillis
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07 Nov 2018 11:54 #24528 by Jerry McGillis
2003 jeep tj 4L ... 5V reference was created by Jerry McGillis
On the 5V reference circuit. how much variance can you have ?
I have checked the speed sensor 5.12V . Cam sensor 5.11V .. Map sensor 5.12V. but when i do the TPS sensor .5.66V ??
Cant get the light to go away. have deleted it and it just will not go off ?
Any suggestions as to where to look next will help .

Tks

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07 Nov 2018 13:10 #24532 by chief eaglebear
Replied by chief eaglebear on topic 2003 jeep tj 4L ... 5V reference
I think we may need more info i.e. any weird engine symptoms or codes a higher voltage on maf circuit I don't think is bad or good depending on how computer is interpreting voltages are present and wether their is enough variance to set a code

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07 Nov 2018 13:43 #24535 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
The engine runs fine at higher rpm's. the code i have is ( P0123 Throttle Position Sensor/Switch A Circuit High Input ) when you come to a stop it almost stalls. and some time does.. lacks power at lower rpm's (below 1200 ) not to bad but noticeable .looked like the previous owner had this problem ( code was present when i got it ). with out going to far i changed the tps sensor. the one i removed looked new. this didn't change anything !
kinda new at this sort of stuff . never got into all this electronic crap !!!!!

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07 Nov 2018 13:52 #24536 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
Had a friend to look at it a while back ( he has more knowledge on wiring then me ) we checked conductivity on the TPS wires and they all checked out ok.

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07 Nov 2018 15:13 #24539 by Tyler
Replied by Tyler on topic 2003 jeep tj 4L ... 5V reference
I've seen this before. Wild as it sounds, but the clockspring in the steering column can fail and backfeed high voltage into the TPS signal circuit. :silly: There's a shared circuit inside the PCM between the TPS signal and the cruise control speed control circuit. That's why you're seeing the high voltage on the TPS and not on the other 5V sensors.

The easiest way to test for this would be to disconnect the clockspring harness and recheck for voltages at the TPS. From the diagram, you can either disconnect the clockspring itself, or at C107.

File Attachment:

File Name: jeepc107.pdf
File Size:264 KB


The other way would be to find the speed control pin at the PCM and remove it from the connector, or cut it in a repairable location. Again, recheck your readings afterwards. If the TPS circuit goes back to normal, you can be pretty certain you need a clockspring. ;)
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07 Nov 2018 16:19 #24543 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
Thanks for the tip, will tr this tomorrow, first off will have to check the sensor wire again, thought of something after posting,
when i checked the wires one may have had 5.12V wile the other was 5.66V ???
none the less, i have read that the clock spring can change the readings but no one has ever said how it ties in to the TPS sensor .
will try to check this all out tomorrow and post what i find .

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07 Nov 2018 17:58 #24545 by Tyler
Replied by Tyler on topic 2003 jeep tj 4L ... 5V reference
Yeah, I've never seen a clear explanation on why those two circuits have anything to do with each other. :lol: The last time I saw this problem, I didn't have time to investigate. Flat rate often means I don't get to dig further. :(

As for your TPS readings, I'm guessing you saw 5ish volts on the 5V reference wire, and 5.6ish on the signal wire. Let me know if you find otherwise.

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07 Nov 2018 18:39 #24546 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
Thanks Tyler, will let you know what i find ...

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08 Nov 2018 10:53 #24559 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
Today we are off to a good start,
First thing to do a little backtracking, checked the TPS wires again so I know the readings before going to far, sure enough one is 5.11V, that is what I suspected, the other one was 5.66V.
Took a shot in the dark and pulled the fuse for the horn, this changed the 5.66V to 5.06V,
Could it be that simple ?? I don’t think so, after all it is a Jeep!!!!
Put the fuse back in and the 5.06V jumps back to 5.66V.
Removed the fuse, sensor goes back to 5.06V, tried to remove the code, no luck, no mater what you do the engine light won’t go off, fuse goes back in and on to the clock spring.
Open the steering column, unplug the clock spring, and there we have it 5.06V at the TPS sensor.
Now to delete the code, code erased, now the check engine light is gone, the old girl runs fine.
It appears the clock spring is the problem??
Before I get a new one, do any of you guys think I miss anything?

Thanks for all the help with this, a special Thanks to Tyler for pointing me in the right direction, pointing out how the clock spring does have a connection with the TPS.

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08 Nov 2018 11:01 #24560 by Tyler
Replied by Tyler on topic 2003 jeep tj 4L ... 5V reference
Awesome! :woohoo: This is enough evidence for me. Clockspring time. Or just live without the cruise control! :silly:

Just curious, which fuse did you remove, specifically? Wanted to go see what the connection is on the wiring diagram.

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08 Nov 2018 17:01 #24575 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
Pulled the fuse for the horn,
jeep not equipped with cruse , but figured the horn & air bags were the only ones going through the clock spring .

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08 Nov 2018 17:05 #24577 by Tyler
Replied by Tyler on topic 2003 jeep tj 4L ... 5V reference
Gotcha. ;) Let us know how the clockspring replacement goes!

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08 Nov 2018 17:14 #24578 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
finding one maybe the hard part ..
local suppler not having much finding one, but a jeep place i deal with said they can get one from a suppler but may take some time, their good as long as you are not in a rush.

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09 Nov 2018 07:19 #24588 by Noah
Replied by Noah on topic 2003 jeep tj 4L ... 5V reference
Sounds like it's time to take a trip to the junk yard ;)

"Learn, apply, repeat."

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14 Mar 2019 12:15 #27811 by Jerry McGillis
Replied by Jerry McGillis on topic 2003 jeep tj 4L ... 5V reference
A long time finding a reasonable priced clock-spring, but got one from Rock Auto , got it installed yesterday, ( wasn't in a rush as the toy was parked for the winter ) tested the circuits, all test fine , fired it up and runs much better at an idle, the engine light is gone ,
Thanks to every one for the help, would never have found this with out the help.
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14 Mar 2019 12:33 #27812 by Tyler
Replied by Tyler on topic 2003 jeep tj 4L ... 5V reference
Niiiiiiice. B) Thanks for the update!

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