Throttle Position Sensor Autopsy Gen3

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Throttle Position Sensor Autopsy Gen3

Post by raYzerman »

I posted this up on FJROwners as I had promised a member there, Slim Pickins (not THAT Slim Pickens) I would autopsy his TPS. He had replaced it on his 2013 (I don't know the mileage, but not that much), and it cured all his throttle response problems. I want to document this here in the Tech Section for future reference and perhaps will add to it if there's any new information comes to light.
A copy of my post......

First, I tested all the circuits with each other by using an analog ohmmeter, and noticed no real anomalies in resistance or the smoothness of increases/decreases... what I was looking for was a jump or flat spot or ??
Next, I did the same to a brand new one I have in my stash, pretty much mirrored the older one....... now, how to take it apart.....
I noticed a line, which is really what appears to be a cap sonically welded on, so cut all around that line with my Dremel and metal saw blade. Interesting, there's a cap all right, with a gasket all around it. Notice brass bearing in the "cap" which fits into the actuator shaft in the middle of the blue. Not shown here is the other end of the actuator, there is an o-ring type seal on that end too... this thing is definitely waterproof.

Image

Notice the 4 well soldered contact points to the terminals... debated unsoldering those, but thought, what if I just pry up on the blue thing.....

Image

Well, that was easy! So now we expose the two sets of double contacts, note the four little "fingers" on each contact, which then rub on the "circuits". Up close they look like little back scratchers as the tips are bent such that they are "fingernails" if you will. If you're a genius, you can figure out the circuits and how they are all related... don't hurt your head, LOL.
So next, I took the best closeup I could, and you can see the little 4 finger tracks in each circuit..... these "circuits" are a smooth as glass, I can only presume they are some kind of resistive material like ceramic.
Now, I could not see any anomalies here either, the "tracks" were very minor (normal?) and given there are 4 fingers to give a better chance of picking up a good "signal" and spreading the load, so to speak, I'm not sure why replacing this TPS would have solved a problem....

Image

Image

Sorry no pics, but I got my magnifying glass out and turned the parts at various angles to get the light in various positions..... don't know if you can see it in the pic but the top band has only three "tracks" even though there are four "fingers". I looked at each group of fingers to see if one was "bent" in such a way not to make as good a contact, but found the opposite, in fact, the two outside sets of fingers should have had more force making contact than the middle two sets... not sure why only three traces instead of four, maybe that stuff is harder than we know. The traces are very faint, not as if they are "digging in" or wearing grooves like your old vinyl LP's.
I'll make an assumption that as long as any contact is being made by at least one or two fingers it should be enough. I have to believe there's some overdesign at play here, but who knows. We simply aren't the engineers who would know.
I'm not saying it wasn't a problem, but it doesn't look like it should have been. Let's just say, perhaps more autopsies might be helpful in that regard. I'm going to look at it again tomorrow with fresh eyes and see if there's anything else.... meanwhile, float up some theories if you got any.....
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Re: Throttle Position Sensor Autopsy Gen3

Post by FJRoss »

Good stuff. I seem to remember that Mr. Beam did a pretty detailed post-mortem on a Gen III TPS a few years back. The trace looked good except when the light was from just the right angle. (Link to the "other" place.)

https://www.fjrforum.com/topic/169700-a ... nt-1335435
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Re: Throttle Position Sensor Autopsy Gen3

Post by raYzerman »

Ross that was only a couple of years ago and I had forgotten... even that I was a participant in the discussion. However, I'll say that particular TPS had significant wear, whereas the one I have doesn't appear to have significant wear. But I will take another look tomorrow.
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Re: Throttle Position Sensor Autopsy Gen3

Post by bill lumberg »

Makes me corporate hadn’t made them send my old assembly off the 2014 back. As much headache as it caused me, I wanted that part.
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Re: Throttle Position Sensor Autopsy Gen3

Post by ionbeam »

Starting in '13 the FJR got a Fly By Wire throttle body system. As part of the TB updates, a new design Throttle Position Sensor was added and moved to the left end of the throttle body rack. By 2016 it is looking like there are some of the new design TPS which are going bad. red2kcbr diagnosed his driveablilty problem as a bad TPS and changed it with a new part. This fixed his driveablity problem so it strongly indicates the TPS was defective, red2' sent me the TPS so I can take a look at it.

The physical construction of the TPS is different than the previous type used on all cable controlled throttle body racks but the electrical design remains the same.

The bad TPS that red2' sent me was P/N 2S3-85885-00. The FSM says the TPS should be 1.20-2.80 k Ω and the sensor output should be 0.63-0.73 V at idle. The old TPS had only one output, this TPS has two outputs. This is the schematic view of the TPS:

Image

The colors of the pins in the connector correspond to the wires. The sensor (item 103) has two resistors in parallel with two wiper outputs. The blue wire is a +5 reference voltage from the ECU and the Black/Blue wire is reference voltage ground. The right side of the diagram is the ECU, the wires make no other stops between the sensor and the ECU. The resistors in the bad TPS measured 1.86 k Ω The wiper value went from 0.380 Ω to 1.86K Ω which is correct for the part.

Top view of the TPS with a blue dot. Dunno what if anything the dot signifies. The metal sleeved holes allow the TPS to be slightly rotated to calibrate it for idle voltage.

Image

This side connects to the long center rod that the throttle plates are connected to and it is different than the previous TPS connection. The center pivot rotates 90°. As the throttle plate rod turns it rotates the wipers inside the TPS in lock-step with the plates. The lobes of the center pivot are not symmetrical so it can key onto the throttle plate rod in only one way.

Image

Here is a family picture when the sensor is taken apart.

Image

The item in the upper left is the cover for the sensor, the green arrow points to the self centering pivot that keeps the wipers turning in circular alignment. The orange ring on the right is a weather seal that goes between the cover and the body of the sensor. In the center of the picture is the main body of the sensor. The yellow arrows point to the wipers which ride along the resistor patterns and pickup a varying voltage off of the circuit. The back side of the plate with the wipers is the keyway which goes on the throttle plate rod. In the upper right is the resistor board, it is upside down, it normally faces down over the wipers. I had to clip the leads which leave the board and go to the connector pins. The blue board is in two layers, the pins connect to the resistor material with an internal connection at the squares which the red arrows point out.

Image

As the throttle plate rod rotates the wipers are dragged along the resistor trail. When the wiper is at one end of the trail it sends ~.0680 volts to the ECU. The ECU converts the voltage to a digital value, does some math and recognizes this as the throttle plates being 17% open. This is the 17 you can read in DIAG when testing the TPS. As the throttle is opened up the wiper voltage goes up to ~4.5 volts, the ECU does some math and recognizes this as the throttle plates being 100% open. The voltage should linearly go up and down as the wipers slide over the resistors.

Pictures showing what is wrong with the resistors was problematic to get. The resistors are failing the exact same way as the TPS that I had in my '04 even though they are different physical materials. Picture attempt #1 to show the worn resistor material issue in a way that retains relationship to the part:

Image

The arrows point to spots along the resistor where the wipers have cut into the resistive material. Once the resistor material gets thin and/or cut it becomes very susceptible to heat causing the resistor value to drift causing erroneous voltages or the wiper simply makes no contact and the voltage drops below 0.680 V which the ECU sees as closed throttle plates. The voltage climbs as the throttle is opened, the ECU sees the throttle opening 20%, 25%, 30% then suddenly going to 0% then as the wiper gets back on good resistor material it suddenly jumps from 0% to 35%. You feel like the throttle was cut and then snapped open creating a really rough ride.

Picture #2 below is taken at an angle so the glare can show just how cut up the resistor material has become:

Image

The deepest wear happens where the throttle is most commonly used. Typically it is at idle and then roughly at 30%-40% of throttle opening where you cruise. The failure of the TPS is a slow wear-out and not a sudden break down. Edit to add: The right side pair of wipers go from the bottom of the sensor (idle) up to the top (WOT). The left side goes from the top (idle) to the bottom (WOT). Both right and left resistor tracks had heavy wear from idle to ~40% throttle.

Beginning TPS failures may only show symptoms when hot, and this is hard to diagnose; as the TPS continues to degrade it will become easier to measure the failure. red2's TPS had failed, yet at room temperature measuring static resistance it tested good. The Gen III Yamaha Diagnostic Tool should allow a dealer to data log the TPS signal which should immediately and clearly show a failing TPS. Unfortunately, this kind of failure will normally pass DIAG and a passive resistance check.

If there really is a fundamental problem and Yamaha starts seeing lots of failures caused by the materials the TPS is made from there will probably be a Technical Service Bulletin (TSB) put out and a Rev. 2 TPS made available. If the issue is related to a date code, manufacturing plant or batch the TSB would instruct a dealer on how to inspect the part for the code (or dot color) and replace any TPS within the problem batch.

Edit to add 12/18/'19:

You can see the wear in the idle area of the resistive material in Ray's picture below which is just like the TPS I autopsied:

Image
Last edited by ionbeam on Mon Oct 05, 2020 10:08 am, edited 1 time in total.
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Re: Throttle Position Sensor Autopsy Gen3

Post by bill lumberg »

Spot on description. Mine started subtle and over months of riding, grew into a bucking bronco, as I rolled from idle, to what the bike saw as an abruptly closed throttle, then- bam, back into throttle.
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Re: Throttle Position Sensor Autopsy Gen3

Post by raYzerman »

I took another deeper look into the one I have here on the bench, read with interest the linked thread and ionbeam's post, mulled over the theories.... so, my new pics taken of the resistor board (my term) and of the rotating contact mechanism. There is a seal and a wave washer which serves to put uniform and constant pressure to ensure continuous contact with the resistor board. When looking at the board, to me the traces by the fingers are so slight, and I wouldn't call it worn in on this one such that "the resistive material is thin"... I'm having a tough time buying into the idea that such faint traces at such a microscopic level is throwing off the resistance on the one I have. We don't even know how thick this resistance material is, but I'd guess quite considerable relative to any depth those traces might have, again on the one I have as I don't have the others for a side by side comparison. I think the mystery is yet to be solved, or at least better explained.

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Re: Throttle Position Sensor Autopsy Gen3

Post by feejerbob »

My 2015 has a surge issue just when the throttle is applied very lightly. When on the gas it is fine. i am leaning towards replacing the tps. Can you please direct me on doing this. Location and adjustment after being replaced is what i am maily looking for. Thanks in advance.
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Re: Throttle Position Sensor Autopsy Gen3

Post by raYzerman »

You may have the internal fingers wearing into the resistor board.... Go into DiAG and look at the values for the TPS at the low end with throttle closed... if you move the throttle slowly, the numbers should not jump but increase one by one.. initial settings at low end are 12-21 normally, that is should not jump from 12 to 18 e.g, but should go in incremental values.
What you can do is adjust the TPS slightly to have a low reading of say 18-19 to get it off the worn spot. This may help or cure it for now, until it "wears in" in time.

To replace the TPS, it is located on the left end of the throttle bodies, and the lower screw is difficult to remove due to limited access.... some trim off a Torx bit and use a 1/4" box end wrench or a small ratchet that fits in small places..... once replaced, put the screws back in not too tight that you can't adjust the TPS position.... move it until DiAG shows a value of of 12-17. Roll the throttle to wide open and you should have values of 97-102. If both are in range, snug up the screws.
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Re: Throttle Position Sensor Autopsy Gen3

Post by mcatrophy »

feejerbob wrote: Mon Sep 20, 2021 7:02 pm My 2015 has a surge issue just when the throttle is applied very lightly. When on the gas it is fine. i am leaning towards replacing the tps. Can you please direct me on doing this. Location and adjustment after being replaced is what i am maily looking for. Thanks in advance.
You're sure it's not the characteristic of the ECU that as you apply a little throttle, the ECU decides to add a little more fuel, presumably to do its bit to help you not stall the engine?

It's a (mis)feature of the throttle-by-wire setup, and is about the only characteristic that I really hate.

[rant]
It's particularly an issue on my YCC-S bike when trying to hold the clutch slipping when starting from rest. D*mn thing puts on more throttle, clutch engages more, I slacken the throttle, clutch disengages, loses forward drive. Makes life very difficult when doing tight carpark manoeuvres.
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Re: Throttle Position Sensor Autopsy Gen3

Post by Festus »

feejerbob wrote: Mon Sep 20, 2021 7:02 pm My 2015 has a surge issue just when the throttle is applied very lightly. When on the gas it is fine. i am leaning towards replacing the tps. Can you please direct me on doing this. Location and adjustment after being replaced is what i am maily looking for. Thanks in advance.
How many miles you got on it? I'd be pretty surprised to see a 2015 wore out. Sounds a lot like the symptoms Viper Dad has with his and the TPS didn't resolve (and that bike has about 75,000 miles on it).
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Re: Throttle Position Sensor Autopsy Gen3

Post by silverback »

From my automotive days, it seems that middle trace that makes a full loop has something to do with compensating for wear on the resistive surface. I forget the method they used to even out the signal even if one wasn't making contact, but it seemed to make sense back then.

I am also fully surprised that they use an analog sensor. Now days most of them are hall effect (I think..?) and work more like your pair of digital calipers in the sense that there is no physical contact between moving parts.

Maybe this is an idea for the more electronics inclined people. Make a non contact digital sensor with a digital to analog converter to take the place of this Paleozoic era technology.
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Re: Throttle Position Sensor Autopsy Gen3

Post by dcarver »

My 2013, 35k, has horribly lurching, surging, just off idle, making low speed maneuvers difficult. Typical TPS symptoms or no?
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Re: Throttle Position Sensor Autopsy Gen3

Post by raYzerman »

First check the MAP sensor hoses and vac nipple are clear of crud..... if clean, then it's likely the TPS.... I'd first try adjusting the TPS so the contact fingers find lesser worn in spot.... if that works, it will work for a while.... someday, a new TPS may be required.
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Re: Throttle Position Sensor Autopsy Gen3

Post by FJRoss »

raYzerman wrote: Fri Sep 24, 2021 10:47 pm First check the MAP sensor hoses and vac nipple are clear of crud..... if clean, then it's likely the TPS.... I'd first try adjusting the TPS so the contact fingers find lesser worn in spot.... if that works, it will work for a while.... someday, a new TPS may be required.
Agreed.

I had not heard of "crud" issues in the vac lines being an issue in Gen III bikes although it was pretty common in the Gen II (especially in '06-'08 or so). Still, it is an easy thing to check - easier and cheaper than swapping out the TPS.

To be honest, the issue sounds more like the TPS than the symptoms I had when the line going to my MAP sensor was plugged on my '07. In that instance, the bike wouldn't idle properly - stalled unless I applied a bunch of throttle. Not just an issue at low throttle openings. (I would also expect a plugged pressure sensor would throw a code - it did on the Gen II.)

Haven't heard much about the TPS issues in more recent years. Was this just an issue with earlier Gen III? (Is there a superseded part number for the TPS?)
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Re: Throttle Position Sensor Autopsy Gen3

Post by dcarver »

Thank you two Ray and Ross for responding. Will do as advised. Naomi does have Ivan ECU flash, was thinking it might be the issue. But will try all alternative first.

Thanks again guys.
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