Living with Code 25/26

[MattSTlouis]

Did it ever cross your mind, that it may not be a good idea to ride the bike while your jumping the data port?
Those instructions were for the bike sitting on a table lift for diagnostic work, not riding it.
You may be harming your bike.
Just saying.

Of course it occurred to me but my magic wand that fixes ECUs is not working right now. If I jump the dataport and it fries the the ECU, I can just grab one of my backup ECUs, I even keep one in the saddlebag. I even got my 1000 mile iron butt cert with the dataport jumped. I've checked the wires continuity from the knock sensor to the ecu, switched the knock sensors, replaced the one throwing the code with a new one. I've even tried to pull the only ground that appears to not be for anything but the knock logical ground and nothing.

I've always got my trusty Harley if the ST blows up. I'm also picking up another ST tomorrow so I have plenty of backups.

 

[rdmnt2002]

Ray,

It was my experience that anytime the revs went above 4,200 RPM for a few seconds, either while riding or in my garage, it would trigger the ECM code 25. To me, there was a noticeable reduction in power when it happened for the first time. In my garage, once the fault was triggered the rpms would drop 500 - 750 rpm even if the throttle was held steady.

I checked wiring continuity and had no circuit faults. Then I swapped the left and right sensors and it still threw ECM code 25. After checking the battery/alternator voltage and all the grounds, and the problem recurred, I knew then it was the ECM itself. Once I replaced the ECM, I no longer experience the fault.

I elected to go the replacement route because of the reports provided by Larry aka @Igofar . Obviously, others have not. Presently, no one is quite sure why the error code 25/26 occurs. Perhaps one day we'll know and someone will develop a "fix." New ECM's are extremely rare to non-existent, so there's not much you can do about if your ECM goes bad.

I felt fortunate when I found a new ECM through Webike Japan. It cost me around $1,200, but it was cheaper than buying another bike.

Chris
[/QUOTE

Thank you so much for the informative response. I appreciate it.

Ray

 

[Gus1300]

You’d probably find if you replaced your lower sub wire harness, and repaired that damage that your ecu was operating normally

Probably but I am not that deep into it right now and am ok with riding it as is for awhile longer until I get to it. As to why it melted is yet another issue...

 

[Igofar]

Of course it occurred to me but my magic wand that fixes ECUs is not working right now. If I jump the dataport and it fries the the ECU, I can just grab one of my backup ECUs, I even keep one in the saddlebag. I even got my 1000 mile iron butt cert with the dataport jumped. I've checked the wires continuity from the knock sensor to the ecu, switched the knock sensors, replaced the one throwing the code with a new one. I've even tried to pull the only ground that appears to not be for anything but the knock logical ground and nothing.

I've always got my trusty Harley if the ST blows up. I'm also picking up another ST tomorrow so I have plenty of backups.

I see everyone recommending to switch the knock sensors to see if it changes anything?
Switching the sensors would not do anything if it was the sub wiring harness that the sensors are connected to that is damaged or bad.
I've corrected a couple ECU/Knock sensor code 25 issues by replacing the damaged sub wire harness.

 

[Igofar]

Probably but I am not that deep into it right now and am ok with riding it as is for awhile longer until I get to it. As to why it melted is yet another issue...

When the bike goes into limp mode, it can cause excessive heat, thus melting stuff.
I find melted switches like this all the time when folks keep riding them with the lights on etc.
Find/Fix the issues instead of throwing solutions at the problems.
Check your lower wire harness.

 

[MattSTlouis]

I see everyone recommending to switch the knock sensors to see if it changes anything?
Switching the sensors would not do anything if it was the sub wiring harness that the sensors are connected to that is damaged or bad.
I've corrected a couple ECU/Knock sensor code 25 issues by replacing the damaged sub wire harness.

Have you ever replace the sub harness where a meter showed good continuity and the plugs looked good and it fixed the problem? If you think it will work then I will give it a try, I trust your opinion over most people.

 

[aniwack]

Let me jump in here and clarify further since I did that voice to text thing running between calls. The bikes in question were all serviced with throttle body sync and major work done on them. The owners opted to keep the existing ECU's due to lack of availability. The owners HAVE NOT VERBALIZED TO ME any lack of performance loss. They also don't ride at 110 mph and 6000 RPM.
So far the engines have not acted up but I'm the mechanic the owners haven't said how much RPM loss they experience.

Here comes the disclaimer: YOUR EXPERIENCE MAY VARY.

 

[Igofar]

Have you ever replace the sub harness where a meter showed good continuity and the plugs looked good and it fixed the problem? If you think it will work then I will give it a try, I trust your opinion over most people.

Yes I have.
Twice
And a $65 dollar harness is a much cheaper repair. It’s cheaper to fix the damaged stuff that keeps frying the ECU units, than using up spare ECU units.
A couple members replaced their ECU and their light went away for a while, but came back again later.
This speaks volumes of something damaging the ECU units over them just going bad by themselves etc.

 

[Gus1300]

I find melted switches like this all the time when folks keep riding them with the lights on etc.

Obviously at one time it got too hot to result in that kind of damage, but I don't continue to ride with the light on/in limp mode...never have, never will. In my experience, there is a distinct sound/feel/throttle response/mileage difference of the bike when the light comes on while underway, and when it is again reset, while underway. So I try to keep my riding style so that the light doesn't illuminate/bike doesn't go into limp mode; that gets me 69mph which is plenty on the route to/from work that I primarily ride. Occasional short duration excursions above the trigger RPM (to get around ppl traveling at a similar speed, for example) don't cause the light to illuminate and result in no difference in feel/sound/throttle response/mileage vs the change in all of those when it comes on because the time/RPM limit trigger was met.

I'll look at the sub harness; as stated, this time around my main focus was the forks and brakes, so wasn't that deep into the repairs...yet. I'd welcome not having to deal with it and will report back when I get to that part swap as to whether it resolves my code issue with the current, or the past that I still have, ECU. It does make sense that the ECU wouldn't be 'fried' because of a sensor issue, so hopefully that IS in fact the problem and not the ECU itself. I just haven't gotten there yet to know.

 

[Igofar]

Just something to think about....
Just because its not throwing the warning light, does not mean that a possibly damaged wire harness is sending confusing signals to the ECU while the bike is running, regardless of speed or RPM etc.
In the beginning, it may only be tripping the light when the RPM is above 4200, but as the unknown damage gets worse, it could start causing more, or different issues.
While it may be a defective or heat damaged ECU unit, if you replaced it, and the next one went bad too, that tells me there is something else going on, and to look further into the issue.
SUB-WIRE, ENGINE
32109-MCS-700
Retail Price: $73.28
Your Price: $56.42

Honda 32109-MCS-700 - SUB-WIRE, ENGINE : Ron Ayers

www.ronayers.com

This may or may not help, but it would be cheaper than toasting another ECU that is almost impossible to find now.

 

[NCBlueST]

I just got the code 26 for the first time. 2004 model, 16K miles. I rode all day in the mountains, often at high RPM. Then at about 220 miles on the day, I got on the highway for the return home and almost immediately got the FI light. I had remembered this as a known "issue", so I rode the remaining 80 miles or so home and perceived no change in engine performance, etc. That's when I pulled the code and found 26 as the culprit. For the record, I did the rolling engine kill a couple of times in that 80 miles, and it cleared the FI fault... briefly. It returned within a few minutes.

So, is the suggestion, beyond checking the 5-way, etc. that I also replace the sub-harness indicated above as a precautionary/potential solution?

 

[Larry Fine]

So, is the suggestion, beyond checking the 5-way, etc. that I also replace the sub-harness indicated above as a precautionary/potential solution?

Check the wiring from sensor to main harness connector first. Any damage should be visible.

 

[RobbieAG]

So, is the suggestion, beyond checking the 5-way, etc. that I also replace the sub-harness indicated above as a precautionary/potential solution?

See my thread for a list of things to check and what fixed it for me (NOT the ECU).