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another TPS thread... wiring info?


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29 replies to this topic

#1 misledxcracker

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Posted 16 March 2007 - 12:34 AM

I had a previous thread, but I figured heck, why not start a new one...

I got code 25 on my '86 GL SPFI coupe a couple/few weeks back. Oddly, sometimes it'll come on, and sometimes it wont. When it does, oh boy is there a dead spot when I floor it... when it's not on, I'm flooring it without a hitch all day :lol:

Previous thread I posted about the TPS, Gloyale gave me some awesome tips... I tested the TPS and the terminal B wire... and it came up good, but I figured hell, why not have a spare, who knows... So I got another JY unit, and it's also good, I'm STILL occasionally getting a code 25. I could run the car until the light comes on, pull up in a parking lot, shut 'er off... wait a minute, start the car... and the code doesnt reappear for another period of time... ranging from 15 to 30 minutes.

Does anyone know, or have the pinouts so I can check continuity on all four of my TPS wires?

#2 daeron

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Posted 16 March 2007 - 04:56 AM

wow, i totally failed to get to reading the thread until I had already sent you two PMs, heh..

Okay, so youve got a throttle position sensor or circuit code....

The way that the CEL is coming and going, and the way your car runs fine when the CEL is off, almost seems like the ECU might be going into limp mode.. but I DO NOT recall if the CEL goes off while in "limp mode"

What kind of driveline do you have, and what kind of mileage do you get? that might give us an indication, as from what I understand your mileage should be crappy driving around in limp mode all the time..

Anyhow, a bad spot in your TPS would only ever come and go like that, that frankly, if the ECU was ignoring its input as faulty (ie, beyond expected range give other input ranges...)

I just wanted to say these things, in addition to what I've already said via PM.. so bear what I've said here in mind, when you are thinking on the PM, please.. I wrote that unsure of the code check status, and you answered that question here :rolleyes:

#3 misledxcracker

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Posted 16 March 2007 - 05:03 AM

the driveline? 2WD 3AT. mileage? varies, around 17-20, but I dont expect much more (thanks 3AT)

limp mode? must look into limp mode... :burnout:

#4 daeron

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Posted 16 March 2007 - 05:28 AM

the driveline? 2WD 3AT. mileage? varies, around 17-20, but I dont expect much more (thanks 3AT)

limp mode? must look into limp mode... :burnout:


2wd 3at here, i used to get 25mpg no matter how I drove. lately things have been bad, i was driving with a blown headgasket for eight months, and I havent filled up my tank in almost six.... so im unsure of my mileage right now, but i think its poorer, but thats neither here nor there. 25mpg, highway or city.. with my FOOT IN THE ACCELERATOR ALL THE TIME........

I think you are on the right track with your TPS wiring, I cannot say mine is "folded" in any way, even though it does bend back a ways... but I can't help you any more with the pinout, Id'a thunkt it was in the FSM :-\

#5 daeron

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Posted 16 March 2007 - 05:45 AM

FSM chapter 2, section 7, page 32 is the ECU pinout. Don't be alarmed that is only shows two pins for the TPS, one of the pins on the sensor is your idle switch, and the other feeds the idle switch.

I am looking for where I first read about the limp mode, anyone who wants to chime in with more than the vague info I have given in the thread here, feel free :)

Page 62 might come in handy, too.. and I can't seem to find much info in the FSM about limp mode, try searching the term...

#6 misledxcracker

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Posted 16 March 2007 - 05:48 AM

found the pinout! thanks daeron!

now for some cursing and making dire attempts to operate the meter :lol:

#7 robm

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Posted 16 March 2007 - 11:34 AM

TPS could be flaky, and give bad readings as it heats up, then "get better" as it cools. Hence the intermittent codes, along with intermittent flat spot.

Test the TPS when the CEL shows and the flat spot is evident. Keep the meter with you, and pull over and test it when it shows up. Practice first in the driveway, so you can do this fast at the side of the road, even if the CEL is not showing.

Good luck.

#8 Gloyale

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Posted 16 March 2007 - 11:41 AM

So you've tried 2 TPSs' and still the same thing? Sounds like wireing or bad connection issues. I will post excact wire colors, pin locations and resistance values tonight. Could be a bad connection to the ecu. When those pins get screwy it's really hard to figure out.

#9 misledxcracker

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Posted 16 March 2007 - 02:13 PM

So you've tried 2 TPSs' and still the same thing? Sounds like wireing or bad connection issues. I will post excact wire colors, pin locations and resistance values tonight. Could be a bad connection to the ecu. When those pins get screwy it's really hard to figure out.


Awesome! :headbang: I got three of the wires located already, I just need the fourth one...

I'm pretty sure that the fourth one is a ground, but which one? :)

#10 Gloyale

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Posted 16 March 2007 - 08:01 PM

here's a reference for other people with TPS problems... i'm sure i'm not the only one :lol: (thanks daeron for pointing out the page number to me in the FSM)

on the ECU there's three yellow connectors... one of them has 24 pins (labelled F106 on the page), this is the one with the TPS wires...

pin number 24 (LG) is the idle switch wire... pin number 25 (W) is the signal wire for the TPS... and pin 26 ® is the power wire for the TPS.

I'm pretty sure that the fourth one is a ground, but which one? :)


Are you looking in the 86 FSM? I went to that page and found something different. I did however find daerons page numbers match the 88 FSM. The wire colors and pins you describe match the 88 as well. And wire collor is different at the ECU between 86 ans 88. I don't have an 87 FSM. Unfortunately, the 86 FSM does not give a numbered pinout of the ECU connectors. I am going to try, by compareing the 2 to figure out which wires you need. It seems the pin locations are the same but the wire colors are different.

Here it is:
+ to TPS= Green w/Yellow stripe at ECU pin 26, Same color at TPS, Same color at check connector under dash(9 pin, white, not red) in the corner of plug

Signal wire= Green w/White stripe stripe at ECU(pin 25), same at TPS, same color at check connector(9 pin,white, not red) middle row, edge.

Idle switch wire= Green at ECU. This one is tough. 86 FSM shows 2 green wires at the ECU. One at pin 9, one at pin 20. In 88 those pins go to diffenernt sensors(MAF and Crank sens. respectively) 86 FSM show the wire as Lt. Blue w/ Green(LG) at TPS, but changes to solid green at big round engine connector, continues as solid green to the ECU and to Check connector. Different check connector than other 2. this one is the big one by the drivers strut under hood. Green wire right under lock tab. It is possible that the 86 FSM has a misprint, I've seen it before. Confirm that that wire chages to solid green by looking at the big round connector by battery. Find the Lt.Blue/Green(LG) wire on engine side of connector, and see if the corresponding wire is solid Green(G) If it is different color, look for that color wire at the Check connector, middle pin. And at the ECU. It should be same color wire from that engine connector all the way to the ECU.

Gound wire= Blackw/ red stripe(BR) shares ground with the rest of the engine harness. There are 3 BR wires at ECU and all should have ground, they are all connected at one point or another. I would check that the Ground wire bolted to intake manifold has a solid connection as the ECU gets all it's grounding from there.

Unplug ECU and TPS and test for continuity between. Test between ECU and check connectors, and TPS and check connectors, check continuity across both sides of that big round connector by battery. I am interested to hear how this turns out.

BTW, Pin 24 in the 86 FSM is for the Temp sensor for ECU White w/ Black stripe(WB).

#11 misledxcracker

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Posted 17 March 2007 - 08:47 AM

Alright, I finally tested the TPS right... I must have been doing it wrong last time...

i checked continuity between terminal B and ground and got between -00.6 and -00.8

i checked between terminal A and B and got -1

i checked between that green wire on the check connector and terminal B and got -1

my meter shows 1 on the left side when no leads are touched, but -1 is the same thing, just with the negative sign...

BOTH of the TPS's do this... does that mean both of them are shot?

#12 Gloyale

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Posted 17 March 2007 - 05:27 PM

Alright, I finally tested the TPS right... I must have been doing it wrong last time...

I have a feeling you are still doing it wrong. no offense. I summed it up below but I will address you're findings individually first.

i checked continuity between terminal B and ground and got between -00.6 and -00.8

Terminal B is the ground wire terminal. Continuity to ground with the TPS mounted is incidental.

i checked between terminal A and B and got -1

Well you should just get 1 or infinite. Until the throttle is opened slightly, then full contact Zero ohms

i checked between that green wire on the check connector and terminal B and got -1

Green wire at check connector should have Zero resistance with Terminal A not B wire of haness. But harness measurments should be done with the ECU and TPS connectors unplugged, otherwise you could be measureing resistance of the ciruits inside ECU.

my meter shows 1 on the left side when no leads are touched, but -1 is the same thing, just with the negative sign...

you should not be getting Negative Resistance values. 1 means infinite resitance, or a total open circuit, no conductivity. -1 means the meter is tring to read a resistance that is off the scale. You should set your Ohm meter to a higher scale like 10 or 20k ohms. The values you are trying to read are between 1k ohm and 10k ohms.

BOTH of the TPS's do this... does that mean both of them are shot?

Are you testing it with the connector unplugged? Here's what it shuold be. Testing TPS itself, not plugged in.

Restistance between A(idle) and (ground) should be Infinite at throttle open, 0 or near zero (.1 ohm or less) at throttle closed.

Resistance between B(ground) and D(+V) changes with throttle opening between 3.5 to 6.5K Ohms

Resistance between B and C(signal V) changes with throttle opening. Less than 1K Ohm at closed, Greater than 2.4K ohms with valve fully opened(80% of resistance between B and D) Restistance should increase and decrease continuosly and smoothly between B and C.

To check the harness, you'll need long test leads. Unplug TPS and ECU connectors. Connect one lead to the tps plug terminal you want to test. Connect the other lead to the corresponding terminal on the ECU plug. There should be Zero or very near resistance. Full continuity. Same method for testing continuity between check connectors and corresponding ECU and TPS pins of harness.

Did you figure out the idle switch wire issue? Is it a Lt.Blue w/Green(LG) at TPS, then Green after the big round plug? You said you found a green one at the Check connector? center pin under lock tab? That would mean it is green at ECU as well.

edits in red

#13 misledxcracker

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Posted 17 March 2007 - 06:33 PM

I'll take it to a shop. Tired of trying to hunt down this problem when I completely hate electrical in the first place.

Some people just cant pick certain things up, electrical stuff isnt my thing.:rolleyes:

#14 Gloyale

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Posted 17 March 2007 - 06:44 PM

I'll take it to a shop. Tired of trying to hunt down this problem when I completely hate electrical in the first place.

Some people just cant pick certain things up, electrical stuff isnt my thing.:rolleyes:


You've got a better shot of actually getting it fixed with help from USMB than taking a 20 year old car to any shop in So. Cal.

BTW when I said there should be continuity to ground at B terminal of harness. When the harness is plugged in, and the idle switch is activated, then continuity exists wih Terminal A, this is the green wire. Without the tps plugged in there is no connection between ground and the green wire.

#15 misledxcracker

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Posted 17 March 2007 - 06:58 PM

Now I kinda think I get it, maybe I was doing it wrong. Correct me if I still am. I have to put this in more simple terms, as I'm idiotic in this subject. I'm not afraid to admit that :lol:

As a matter of fact, I'll print this once it's official that I am right :lol:

OK...

Turn car on. dont start it, right?

Unplug connector, use TPS pins, not harness pins

Check terminal A and ground for continuity, i should get infinite... then I crack the throttle open some, and should get good continuity.

Terminal B and D should be between 3.5 and 6.5 with opening/closing of the throttle.

Terminal B and C should be less than 0.1 when closed, greater than 2.4 when open, and should go gradually down with gradual letting go of the throttle

Then yeah, the wiring, I think got that part. Use the FSM for reference on the ECU pins, test for continuity from the harness to the pin on the ECU, using long leads. I have those.

Correct away, if need be :headbang:

#16 Gloyale

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Posted 17 March 2007 - 07:27 PM

Now I kinda think I get it, maybe I was doing it wrong. Correct me if I still am. I have to put this in more simple terms, as I'm idiotic in this subject. I'm not afraid to admit that :lol:

As a matter of fact, I'll print this once it's official that I am right :lol:

OK...

Turn car on. dont start it, right?

Unplug connector, use TPS pins, not harness pins

Check terminal A and ground for continuity, i should get infinite... then I crack the throttle open some, and should get good continuity.

Terminal B and D should be between 3.5 and 6.5 with opening/closing of the throttle.

Terminal B and C should be less than 0.1 when closed, greater than 2.4 when open, and should go gradually down with gradual letting go of the throttle

Then yeah, the wiring, I think got that part. Use the FSM for reference on the ECU pins, test for continuity from the harness to the pin on the ECU, using long leads. I have those.

Correct away, if need be :headbang:


ignition switch doesn't need to be on.

between B and C should be less than 1 ie .999 or less

As far as the FSM. The pin location for the idle switch wire is changed 87 and after. So if you're using 87+ FSM it will show different pin.
You're 86, Idle switch wire(G) wil be at either pin 9 or 20. I really wish they numbered them in 86. it shows color and location, but not specifically which pin for each. so it could be either of those 2 green wires. Really man. I'm pullin for ya. I really think the intermittent nature of the issue points to harness or connection issue.

#17 daeron

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Posted 18 March 2007 - 04:51 PM

so how is it going here?

(thanks Gloyale, BTW.. I was helping him before I went to Sebring, BUT you have ALOT more experience under your belt than I do, and your assistance has probably been much more help to him than mine :-p)

I was also in a complete FUNK until I got to the race, so my communication skills were somewhat lacking.. anyhow, Cracker, do you think you are getting things figured out now?

#18 misledxcracker

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Posted 18 March 2007 - 06:36 PM

terminal A and ground, no continuity with throttle open or closed

terminal B and D was between 6.50-9.50 opened/closed

B and C was between 3.00-5.00 opened/closed

i set the meter at 20k ohms, no other setting would register at all

bad TPS? me still doing it wrong?

#19 Gloyale

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Posted 18 March 2007 - 07:04 PM

test between A and B of TPS. shuold be continuity closed, none open. with it unplugged. this is the idle switch portion. If you can't get continuity between A and B ever, throw that TPS away. one thing however is that those contacts close at hte very end of the travel of throttle. you may have to loosen the TPS screws, and turn it a little so that the contacts can fully close. That's what the whole feeler gauge thing is about in the FSM. Should be conmtinuity at closed, but with just a crack open, should be none. If it's out of adjustment you're idle switch won't ever make contact so try that. Hook up test leads to A and B and move the TPS around a bit. If you don't ever get continuity then that one is shot.

Did you get same readings on both TPS? Those other numbers don't seem good to me. seems they are all higher than normal resistance.

20k Ohms setting is perfect. You're on the right track. test the other one. Doesn't need to be installed to test. Just do the continuity tests between terminals. use a screwdriver to act as the throttle shaft turning.

#20 daeron

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Posted 18 March 2007 - 07:08 PM

you should be testing resistance between terminal A and ground, as in.. terminal A and terminal B. not as in, terminal A and your thermostat housing/strut tower/negative battery cable.

When you unplug the TPS it isnt connected to the ground wire, so it isnt grounded out. The TPS basically connects terminals A and B as soon as the throttle is open, and the ECU is looking for a grounded wire there as a sign that your foot is not on the gas.....

That make sense? if so, re explain it to me. Otherwise I can go on at more length to try to help you, but my brains are still mushy from Sebring so I may just be more confusing than helpful :banana: If you want, I could go on, but I'm cutting this post short.

#21 Gloyale

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Posted 18 March 2007 - 07:53 PM

you should be testing resistance between terminal A and ground, as in.. terminal A and terminal B. not as in, terminal A and your thermostat housing/strut tower/negative battery cable.

When you unplug the TPS it isnt connected to the ground wire, so it isnt grounded out. The TPS basically connects terminals A and B as soon as the throttle is open, and the ECU is looking for a grounded wire there as a sign that your foot is not on the gas.....


You nailed it in terms of describing how to measure terms A and B. except you got it backwards. Switch is closed(grounded) when throttle is closed. When you open the throttle it opens the switch. I mixed up and posted wrong earlier in this thread. I corrected it later in red.

Throttle closed= zero ohms, full contact
throttle open= infinite, no contact.

#22 misledxcracker

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Posted 18 March 2007 - 08:19 PM

on one TPS, i get continuity from terminal A to B now, from simply unscrewing the top screw.:lol: when i tighten it, no continuity.

on the spare, no continuity at all, so i guess junk that one.

All the resistance on the other tests are higher than normal, though. and thats on both of them :-\

#23 daeron

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Posted 18 March 2007 - 08:34 PM

on one TPS, i get continuity from terminal A to B now, from simply unscrewing the top screw.:lol: when i tighten it, no continuity.

on the spare, no continuity at all, so i guess junk that one.

All the resistance on the other tests are higher than normal, though. and thats on both of them :-\


unscrewing... huh???

my TPS doesnt have any screws other than the ones taht hold it on, and they have nothing to do with any of the measurements of the system.. the only way anything should ever change with the TPS is if the throttle shaft moves.. IE, if you have one off the car, you should have to stick a screwdriver into the hole on the metal side of it and turn the "volume knob" as i like to call it... it should have continuity while closed whether the thing is screwed tightly down or not... if tightening it down changes anything, then youve got a problem there.. when you change the TPS there is a procedure to calibrate it properly based on the resistance reading at certain throttle positions.. you use feeler gauges and all sorts of other lovely crap like that, but I can point you to the FSM section to read how to do that when it comes up.

In the meantime, we need to understand what screw this is that changes your idle switch.... Also, cheap multimeters cannot always be considered the most accurate for resistance readings.. BUT the fact that both TPS units tested about the same does suggest a certain degree of consistency, and it may be that your cheap multimeter isn't that great.. I know I went and borrowed my Dad's Fluke (expensive) specifically to calibrate the TPS I replaced....

Also, don't forget that sitting with the TPS in your hand you can exceed expected ranges; with the throttle shaft stuck into it, and both the mounting screws threaded, you are only given so much range of motion, and that limits the range of resistance you can get. IF you can't spin the sensor one way or the other enough to achieve desired readings, then the TPS needs replacing. That is an odd way for them to fail, though. Usually they just get bad spots on the pot, "crackly areas on the volume knob" as it were..

#24 psylosyfer

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Posted 18 March 2007 - 08:53 PM

http://mshoup.us/doc..._XT_partial.zip
If you download this PDF, You can find all the pinouts and codes in it for your fuel system.

#25 misledxcracker

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Posted 18 March 2007 - 09:00 PM

unscrewing... huh???

my TPS doesnt have any screws other than the ones taht hold it on, and they have nothing to do with any of the measurements of the system.. the only way anything should ever change with the TPS is if the throttle shaft moves.. IE, if you have one off the car, you should have to stick a screwdriver into the hole on the metal side of it and turn the "volume knob" as i like to call it... it should have continuity while closed whether the thing is screwed tightly down or not... if tightening it down changes anything, then youve got a problem there.. when you change the TPS there is a procedure to calibrate it properly based on the resistance reading at certain throttle positions.. you use feeler gauges and all sorts of other lovely crap like that, but I can point you to the FSM section to read how to do that when it comes up.

In the meantime, we need to understand what screw this is that changes your idle switch.... Also, cheap multimeters cannot always be considered the most accurate for resistance readings.. BUT the fact that both TPS units tested about the same does suggest a certain degree of consistency, and it may be that your cheap multimeter isn't that great.. I know I went and borrowed my Dad's Fluke (expensive) specifically to calibrate the TPS I replaced....

Also, don't forget that sitting with the TPS in your hand you can exceed expected ranges; with the throttle shaft stuck into it, and both the mounting screws threaded, you are only given so much range of motion, and that limits the range of resistance you can get. IF you can't spin the sensor one way or the other enough to achieve desired readings, then the TPS needs replacing. That is an odd way for them to fail, though. Usually they just get bad spots on the pot, "crackly areas on the volume knob" as it were..


with the top screw unscrewed slightly, the car runs awesome.

screwed in... it runs like crap.

ahhh this car's making me grey




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