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Discussion Starter · #1 ·
My head is about to explode here. The diagrams are on pages 312, 387, and 388 of the manual - they show all the wire colors but I can't seem to find the function of each wire?

It is part #29 in these screenshots of the diagrams.



 

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The RB ( red/black ) is the power wire. The 4 lines on the right are signal lines from the ECU. Without an o'scope and Yamaha releasing what type of signal they are using , you would never be able to check what they are doing.
All you can really do is insure you have power and make sure the wires are good.
 

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Discussion Starter · #3 ·
I am just trying to manually check if it operates, want to send 12v to it to see if the plunger moves. Basically I just need to know the ground and the power wire color codes.
 

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It looks like they are using case ground, it only shows the power wires and the signal lines.
 

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Discussion Starter · #5 ·
It looks like they are using case ground, it only shows the power wires and the signal lines.
Can't be, I took it out, its all plastic. One of the wires must be ground - there are two red/black wires i wonder if one is ground other power.
 

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It is showing the 2 R/B wires tied together, it doesn't show any ground wire. they are always a black wire, unless they are using the signal lines to supply a ground as the trigger, then they would only need to supply the hot wire.
 

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Discussion Starter · #7 ·
It is showing the 2 R/B wires tied together, it doesn't show any ground wire. they are always a black wire, unless they are using the signal lines to supply a ground as the trigger, then they would only need to supply the hot wire.
Thats probably how it is setup.
 

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That appears to be a set of stepper motors or 1 stepper and position sensor.
ECU provides ground function for operation, usually in that type of system there's only output from ECU when it needs to move it to adjust idle speed.
Like Steve said youll need a scope to view signal.
Scanner (if you have access to one) with live data function will usually display ISC drive in "steps". ECU will drive it to one end and count steps as it learns idle.
I wouldn't put battery voltage on any of the wires from ECU as a stepper motor has a tiny duty cycle and will burn up quickly, could also run on 5 volts.
If there's a position sensor, batt voltage will damage it almost instantly.

Just out of curiosity, what symptom are you troubleshooting?
 

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Discussion Starter · #9 ·
That appears to be a set of stepper motors or 1 stepper and position sensor.
ECU provides ground function for operation, usually in that type of system there's only output from ECU when it needs to move it to adjust idle speed.
Like Steve said youll need a scope to view signal.
Scanner (if you have access to one) with live data function will usually display ISC drive in "steps". ECU will drive it to one end and count steps as it learns idle.
I wouldn't put battery voltage on any of the wires from ECU as a stepper motor has a tiny duty cycle and will burn up quickly, could also run on 5 volts.
If there's a position sensor, batt voltage will damage it almost instantly.

Just out of curiosity, what symptom are you troubleshooting?
Thank you, although a bit too late, I think I may have already burned it, lol. I've started experimenting last night by randomly connecting wires to various pins on the plug, with one of the combinations it vibrated violently for a fraction of a second and stopped, and no longer reacts to any input. I ordered a used throttle body from ebay for $25, so not a big loss.

I'm experiencing RPM drop when closing throttle, have a big thread going on it. 950 idle too low off throttle?
 

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Went back and read the thread.
Nice work馃憤
In automotive systems there's what's called base throttle position, that's what you corrected by adding some air with the plates.
Big diffrrence is Yamaha doesn't address this in its service instructions, Bosch, Delphi and Lucas-Sagem systems that aren't fly by wire all require this to be addressed during service. Will cause the same symptoms if not set properly.
Have seen my share of wonky IAC (ISC) valves in my day as well, ones used on 90's Land Rovers were junk.
 

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Discussion Starter · #11 ·
Went back and read the thread.
Nice work馃憤
In automotive systems there's what's called base throttle position, that's what you corrected by adding some air with the plates.
Big diffrrence is Yamaha doesn't address this in its service instructions, Bosch, Delphi and Lucas-Sagem systems that aren't fly by wire all require this to be addressed during service. Will cause the same symptoms if not set properly.
Have seen my share of wonky IAC (ISC) valves in my day as well, ones used on 90's Land Rovers were junk.
Except now I'm tripping code 37 time to time - incorrect idle speed. Not even sure how it detects it, as far as the ECU is concerned, I could just be holding the throttle grip slightly open at all times.
 

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Discussion Starter · #13 ·
Idle speed and target idle speed mismatch possibly,
see if Ivans can raise the target speed in software.
But there must be some additional logic here, because the ECU should only check idle speed if the throttle is fully closed and TPS voltage set in the closed range. Since my throttle remain open, and TPS is sending corresponding voltage, the ECU shouldn't check idle, unless there is a logic that expects idle when the bike is stopped. I dont really get it.
 

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Three ranges in fuel systems.
Idle, part load and full load.
Traditionally TPS would set the mode.
Some newer vehicles look at VSS (vehicle speed)
along with other inputs.
Would ask Ivans.
 

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Discussion Starter · #15 ·
Three ranges in fuel systems.
Idle, part load and full load.
Traditionally TPS would set the mode.
Some newer vehicles look at VSS (vehicle speed)
along with other inputs.
Would ask Ivans.
Thank you so much! I don't want to bother Ivan, he spend so much time with me already. The way I see it, I'll just deal with the code, the bike is so much more compliant now.
 

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Discussion Starter · #16 ·
Three ranges in fuel systems.
Idle, part load and full load.
Traditionally TPS would set the mode.
Some newer vehicles look at VSS (vehicle speed)
along with other inputs.
Would ask Ivans.

Jaguartech, what are the chances of me burning out the ECU or the new ISC valve by riding with the CEL on constant? I understand the ECU will continuously try to send signal to the ISC to try and close to reduce idle, can it fry itself by doing so?
 

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Most systems will stop trying to move the pintle when it detects no feedback (change in engine speed) and sets the fault.
Most systems that use auxiliary air control valves are designed as such. However, the only way to know for sure is to look at the drive circuit with a scope and see if the ECU is still tryng to move it after it hits the closed position (first hard stop).
Most systems just shut off idle control and will move the valve to the first hard stop when it sees off idle throttle position.

Here's a link to a very detailed description of how most systems are engineered to operate.


Would suggest setting throttle plate position as close to the target idle that the ISC should maintain as possible,
Durind decel idle air valves usually move to the first hard stop. When ECU sees engine speed fall below target speed it will move the pintle back allowing air in.
I would suggest moving throttle plates open just enough to cause the ECU to drive the ISC open by only a few steps instead of the full step count.
Adding more air from the plates instead of relying on the ECU to drive the ISC to pick up the idle may take the dip in engine speed out.
Over/under could be a matter of a couple of thousandths of plate position.
 

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Discussion Starter · #18 ·
Most systems will stop trying to move the pintle when it detects no feedback (change in engine speed) and sets the fault.
Most systems that use auxiliary air control valves are designed as such. However, the only way to know for sure is to look at the drive circuit with a scope and see if the ECU is still tryng to move it after it hits the closed position (first hard stop).
Most systems just shut off idle control and will move the valve to the first hard stop when it sees off idle throttle position.

Here's a link to a very detailed description of how most systems are engineered to operate.


Would suggest setting throttle plate position as close to the target idle that the ISC should maintain as possible,
Durind decel idle air valves usually move to the first hard stop. When ECU sees engine speed fall below target speed it will move the pintle back allowing air in.
I would suggest moving throttle plates open just enough to cause the ECU to drive the ISC open by only a few steps instead of the full step count.
Adding more air from the plates instead of relying on the ECU to drive the ISC to pick up the idle may take the dip in engine speed out.
Over/under could be a matter of a couple of thousandths of plate position.
Thank you. I've been reading a thread on another forum where a member suffering from high idle speed has fried two ECUs, he ended up deleting the ISC completely in the end, and just using the throttle arm stop screw to limit how much the valves can close. The only downside to his solution is he has to hold the throttle slightly open when starting cold engine for 10-15 seconds. I will create an account to reach out to him to see how he went about ECU errors with the ISC absent.


"the ECU looks at the TPS input,crank position input and map inputs and determines ISC position for the best idle speed.

the ISC is NOT designed to have a constant on time, it has a rather limited duty cycle.

IF the idle speed does not do what its supposed to the ECU will keep sending requests and the duty cycle increases to the point where something,typically the ECU,overheats and bites the dust.
 

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I did the same thing to a '90 Ford 5.0 with a manual trans in a truck I used to own, it's problem was the rev's wouldn't fall during shifting and would take forever to fall to normal idle at a stop.
Blocked off the idle passage and set idle speed by the throttle plates.
Worked well, drove it for years like that.
Luckily that ancient system was so crude that it wouldn't fault with the IAC valve unplugged.


Do you have access to a scan tool ?
 

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Discussion Starter · #20 ·
I did the same thing to a '90 Ford 5.0 with a manual trans in a truck I used to own, it's problem was the rev's wouldn't fall during shifting and would take forever to fall to normal idle at a stop.
Blocked off the idle passage and set idle speed by the throttle plates.
Worked well, drove it for years like that.
Luckily that ancient system was so crude that it wouldn't fault with the IAC valve unplugged.


Do you have access to a scan tool ?
I do not, I understand the 950 does not even have a diagnostics port. I'll speak to Ivan to see if this is something that can be disabled by reprogramming the ECU with the software and tools that he has, and I'll also fiddle with the throttle stop screw for finer adjustment where it offsets the ISC settings but without starting to trigger the CEL.

Another crazy idea I've been contemplating is to take the next size drill bit, and expand the size of the port holes the ISC opens.
 
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