Renix TPS Adjustment

 

Before attempting to adjust your TPS, there are a few things that need to be done.

  1.  Be sure the throttle body has been recently cleaned. It’s especially important that the edges of the throttle butterfly are free of any carbon build-up.
  2.  With the KEY OFF, and using the positive (red) lead of your ohmmeter, set on the lowest scale, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself.
  3. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall.

If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. It is covered in detail in Tip 6.

TPS ADJUSTMENT FOR ENGINE ISSUES

Both Renix manual and automatic transmission equipped XJs and MJs have a flat three-wire connector to the TPS which provides data input to the ECU. The three wires in the connector are clearly embossed with the letters A, B, and C. Wire “A” is positive. Wire “B” is ground. DO NOT UNPLUG THE CONNECTORS!Backprobe 2

  1. KEY ON, measure voltage from “A” positive to “B” ground by back-probing the connectors. Note the voltage reading–this is your REFERENCE voltage.
  2. KEY ON, back-probe the connector at wires “B” and “C”. Measure the voltage. This is your OUTPUT voltage.
  3. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts.
  4. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you have achieved your desired output voltage.
  5. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can’t achieve the correct output voltage, replace the TPS and start over.

Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.

TPS ADJUSTMENT FOR AUTOMATIC TRANSMISSION ISSUES

Renix automatic transmission-equipped XJs and MJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as outlined above—FOR ALL ENGINE MANAGEMENT RELATED ISSUES.

However, the automatic TPS also has a square four-wire connector, clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY.

First off, DO NOT UNPLUG THE CONNECTORS!

  1. KEY ON, measure voltage between “A” positive and “D” ground by back-probing the connector. Note the voltage. This is your REFERENCE voltage.
  2. Back-probe the connector at wires “B” and “D”. Measure the voltage. This is your OUTPUT voltage.
  3. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts.
  4. Adjust the TPS until you have achieved this percentage. If you can’t, replace the TPS and start over.

So, if you have an automatic equipped XJ your TPS has two sides–one side feeds the ECU, and the other side feeds the TCU.

For those with a MANUAL TRANSMISSION–the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced. The square 4 wire connector is just not used.

Revised 7/08/17

40 thoughts on “Renix TPS Adjustment”

    1. Yes it will. Thanks for bringing this up.

      BUT, the Transmission side of the TPS is no where near as critical as far as adjustment as the Engine side is.
      The rule of thumb here is you use the Trans side to DIAGNOSE issues with that side of the TPS, but always ADJUST the TPS using the Engine side.

  1. I spoke to soon. I don’t know we’re I posted it but, I thought I had fixed my jeep idle issues with switching in a different tps . That didn’t work after a short drive down the rd. I checked the voltage and couldn’t get a reading on the 17% side or b and c reading so I figured the other used tps was bad too. I then went and bought a new tps. All the voltage readings came out perfect and it did good til the motor warmed up. Jeep still won’t idle. I am really burnt out at this point. Kind of don’t know what to try next. Is there another place to adjust the idle on this thing? It’s got to be something simple cause this things runs like a top off of idle.

  2. I was checking back over everything I had touched mentally today and realized during throttle body cleaning and IAC cleaning that I may have moved something. The kick down cable crossed my mind and I had no idea it did anything with idle. However, I adjusted it while the jeep was idling and now the jeep runs like a top! Guess I moved the cable setting when I unhooked it during cleaning. I am surprised no one else seems to have run into this. Hopefully all my heart ache can help someone else. Didn’t need any new parts just brain power.

  3. Is the setting and adjustment the same for both renix engines:
    2.5L4 TBI and 4.0L6
    each with manual transmission?
    17% of incoming voltage = outcomig voltage?
    Thanks!!

  4. Hi Cruiser54, Thanks for putting this site up and answering questions.
    I have an ’87 XJ Limited Wagoneer with 4.0 and AW4. It has been well taken care of but some of the maintenance has been worked around, such as a momentary switch under the dash to bypass the neutral start switch. 🙂 We have driven it only some 5k miles, now showing 130k. It has always seemed anemic and we were discussing possibilities and the primary driver said it seems the pedal just doesn’t go down far enough. As for the TPS the reference is 5.2V, closed .9V, pedal floored 3V and WOT at the throttle body 4.4V. Electrical questions: At WOT should the output equal the reference?

    On the physical side the pedal does not completely open the throttle plate (lacks about 1/3) before before the arms hits the floor. There is a depression in the carpet so that is likely the problem. Do you remember if perchance there was extra padding or something under the carpet that would restrict the pedal movement?

    Thanks again,

    Dean

    1. Not uncommon Dean. The carpet got in the way. Do what you can to get around that. I’ve actually lifted up on the pedal rather strongly to gain the travel back.
      When is the last time it got plugs, wires, cap , rotor and throttle body cleaned?
      Since it is an 87, I would strongly suggest doing Tips 1,3, 4, 5, and 27. Make sure the intake manifold bolts are tight.
      The vacuum line from the throttle body to MAP sensor has to be perfect also.
      If you haven’t indexed your distributor per Tip 13, that would be a good start.

      1. Cruiser54, methinks thou hath been miss dubbed. If you can bend that throttle rod by hand I really think Bruiser98 would be more applicable. 🙂
        I got but I put a block between the firewall and rod on the top to protect another gizmo than used a hydraulic spreader under the pedal end and it finally acquiesced.

        I would like to eliminate the C101 and index the distributor but that is another day. This is a ’87 Wag and the sight tube for setting the timing opens right onto the back side of the serpentine belt. Does that mean the only way of finding TDC is the “old fashioned” way?

  5. Hey I have a problem with my 1990 renix that I can’t put my finger on. I’m wondering if you can shed some light on the situation. I keep getting a high idle once everything is warmed up and sputtering between 1500 and 2000 rpm. The sputtering is intermittent and occasionally backfires when it is happening. The high idle is almost all the time. Anything you can think of would be awesome before I start ripping everything apart and replacing everything lol. I don’t have a lot of time to start diagnosis on everything in your guide due to work and kid’s so if you could give me your best guess on where to start that would be great! This is my first renix and I have never run into this problem with any of my other jeeps.

  6. First – thanks for these excellent articles. They’ve already been a huge help getting my Jeep back on the road.

    I’m did these tests as part of figuring out a low power condition, and all signs are pointing to the transmission side of the TPS being the issue. I tested the engine plug and made a small adjustment to bring it into range. However the transmission side seems to have zero reading. No power at either terminal and the ground seems bad as well.

    Any tips on sorting this out? I’ve already done some ground upgrades while following your ground refresh article and they seemed to help.

    1. Glad the Tips are helping you.
      The dipstick tube stud ground is a huge player in this. See Tip 1.

      Tip 10 should also be done as well as the Connector Refreshing.

      See what you get for readings at the TPS Trans connector after that.

      Have you done Tip 5?

  7. My ’88 XJ has been idling @ roughly 1200-1500 for a while now. Decided to check TPS hoping that would remedy this.

    I did the ground / 101 / engine bay connector refreshing bit shortly after buying the rig roughly two years ago.

    TPS reference * .17 gives a target voltage of .81v. Found it @ .3v or so. I’m thinking at this point “Voila! I’ve found my problem.”

    Maybe, but after adjusting the TPS my idle jumps to 3500. This being a little high(!) I followed the “high idle after adjusting” tip.

    Long story short, if I set the TPS to any voltage over .4 or so, I get a 3500 rpm idle.

    Bad TPS? Something else I’m missing (a not-unlikely possibility)?

    I don’t wanna start shot-gunning this problem with my wallet (parts-cannon).

    Thanks in advance. (go ahead, I’m prepared to be embarrassed)

      1. Yeah I did, and re-checked the TPS ground before attempting the adjustment. The rest of the grounds were cleaned two years ago, but I was new to the Renix world then… I’ll go back & re-check/clean ’em.

        Reading through the list of tips, I’m going to check a couple other items off the list as well (as time & weather allow). It’s been running rich for a while also, so going to check out the Coolant temp sensor, MAT & MAP before I try the TPS again.

  8. I’m having a slight high idle as well, around 1,000 – 1,200ish when warmed up. I have tried setting the TPS to 17% output putting it at about .827 volts and it still idles high. Then I decided to set it lower (.700 volts) and it idles about 700ish until the throttle is pushed, and back up it goes. If I unplug the TPS while it’s running and “blip” the throttle, the idle comes back down to normal, but will go back up once the TPS is plugged back in and throttle is pushed. This is a fresh 4.7 stroker that runs strong, but doesn’t like to idle normal.

  9. The throttle body was cleaned recently, including the IAC. The throttle stop is set for the smallest movement of the butterfly from touching. I bought another new TPS, added two #4 ground wires (from intake manifold to firewall, and dipstick bracket to a stud below the coil), plus a new battery ground cable to the dipstick bracket. I also soldered a new connector to the group of small wires that go to the dipstick bracket. When checking ohms from ground on the flat TPS connection to the battery, I get almost a perfect zero. I’ve sprayed throttle body cleaner all around with the engine running and didn’t notice any idle change. I even set the TPS down to .500 volts and it still wants to creep up to 1,000 – 1,200.

    I’m at a loss here, but will try whatever is next, possibly a fire, then to the crusher?

  10. My Jee: 89 4.0L auto. I have had the high idle issue for about 2 years now. I refreshed the grounds at the dip stick and the firewall and added 8gauge wires to the ground. I’m on my 3rd AIS motor and 3rd TPS, I put new 4 relays behind the battery, I cleaned all the plug connectors and added diletric silicone at the junctions. My issue is most times the engine would start normal and the idle would go up about 5 minutes on. I shut it and restart, sometimes it would go back to normal and idle at 600 rpm and every once in a while it would race to 3000 rpm. Today I was checking the Ohm reading from the flat switch B terminal and I got 3.7 ohms. How do I remedy this issue.

    Thanks

  11. Thanks, I did tip 5 and the result I got is 3.7 ohms on the B terminal instead of 1 or less. Does tip 6 cover the procedure on how to remedy the ground issue or there is more you can help.me with.

    Thanks

    1. Hats off to Cruiser. After a couple.of years of dealing with erratic high RPM issues, I finally got the time to get the time to work on the wiring harness. I cut and soldered the grounds. So far, I have had no more issues with the engine racing.
      A million thanks, you saved the Jeep!
      I had almost given up. All the items I replaced multiple times were not the cause.
      Thanks again

  12. Hi cruiser54 this website is awesome lots and lots of helpful tips. I have 1990 renix 4.0 replaced every senor in it yea I know but thats how I am lol. Anyway my problem is once is warm driving normal when I let off the accelerator it wants to die then it will catch up and running fine I have tested and checked everything three times or more I’m out of ideas and in need of some help

  13. I have a 1990 with the 2.5L/manual trans….your advice that the automatic transmission TPS will work is incorrect! I bought one and its a very different setup. If I’m wrong…let me know.
    I’ve wasted $12.00 on your word and don’t want to waste any more.

    Dean

    1. I must have misunderstood you then, because I know the 2.5 auto and manual TPSs don’t interchange, but the 4.0s do.

      The website is supposed to notify me as soon as a comment is made. didn’t do it til today.

  14. You have not posted my email about the TPS false claim. I see that you
    are vain and cannot take criticism.

    Please be MAN enough to get rid of the false claim that the auto
    TPS will fit the 2.5L manual transmission.

    Dean

    1. You know Dean, I operate this website, pay for it myself, selflessly try to help folks without any payment.
      Your comment makes me wanna puke.

      I have done my best to answer all of your questions in a timely and accurate manner. MANY questions.
      Oops, I misunderstood something and cost you a measly $12? boo-hoo.

      So you attack me personally?
      Don’t expect any more help from me.

  15. hey cruiser, I appreciate all the info (and to hell with the last guy who gave you crap) and this helped me diagnose my bad TPS today. It is .85v at idle and then as soon as it comes off it drops to almost 0 until about 15% throttle where it performs as it is supposed to, which explains the hard stumble off idle, and hopefully the other running issues, but we’ll see after I run to the parts store. One question I have for you though is why my TPS has 6 wires and both plugs when it is, and has always been, a five speed. The auto transmission plug IS plugged in, and that set of wires dives into the harness and heads towards the firewall and the C101 (which I eliminated as per your instructions.) Any ideas on this? I am the second owner and it most definitely has been a manual its whole life and there is no sign of harness butchery. I am on my way to the parts store to get a new one, and am unsure about whether to get the manual or auto TPS now, since those wires go somewhere… I wonder if there is another input to the computer? or maybe it was just the general harness and those wires terminate in a connector. Either way I figured I would see if you had seen this or had any thoughts? Thanks for everything you do, most of us appreciate it very much.

    1. Sorry for the slow response. The site is supposed to notify me immediately when questions are asked. Kinda spotty.
      Get the auto one. It’s waaaay cheaper.

      Don’t plug the trans side connector to your harness.

      Have you performed Tip 5 and cleaned your throttle body?

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