The CB1100 Community Forum

After much trawling on the Japanese forums I found that this is also a known issue in Japan. I would post links to what has been said but they mirror what has been observed here and it's all in Japanese language.

The key takeaway from an official Japan Honda dealer post is a suggestion to have the ECU reset at a dealer. Here is the content translated approximately:

"For PGM-FI vehicles (with clutch switch)
・The idling rotation does not drop to the specified value.
・The idling speed is lower than the specified value.
There are some irregularities in idling rotation.
In such cases, the following measures may be considered.

● Target: PGM-FI vehicles with a clutch switch
● Event: The idling speed may not drop.
Example CB1100EX 1600rpm
●Cause: When the clutch switch is ON (while the lever is being held), the idle speed is reduced due to the half clutch, and the ECU instructs the ECU to open the IACV to restore the idle speed to the standard value. If that state is repeated several times, improper data will be written to the ECU and idling will not drop to the specified value.
●Correspondence: Reset the ECU (re-learn idling) to return the idling to the proper speed."

Lambchops thanks very much for this enlightening insight into the Japanese forum.

Copied and pasted this part into my collection of tricks to alleviate this issue, two variables here;
1; things come right after the iacv is replaced ( and we don't know why but friction is suspect )
2; a software update solves this problem ( but not available in the us. )

There seems to be a general reluctance from Honda dealers to do a software "upgrade" except for some educated technicians who seem to understand the situation and have found a way to repair the problem, unfortunately the community seems to be running out of techs like that.

Since i like to solve this kind of problem i have tried to find a better solution and although it has not been tried/necessary i think there is a way to access the iacv from the top of the engine instead of removing the rear fender, airbox etc., it involves removing the fuel rail to gain acess to the top of the iacv housing which comes straight off with 3 torx screws and then can be replaced and put back, we did establish that the iacv replacement solves the problem 100% of the time.

But i agree with everybody that says that we solved a software problem with a hardware solution.

Again a big thanks

Thanks Lambchops. So, is “resetting” the ECU a job for a dealer or is there another way?

Very good info Lambchops. Thank you for that!

Max, Is there a way to do an ECU reset without a trip to the dealer? I wonder if my Healtech unit will do one. Research must be done.

It was funny to read your post Lambchops as I ate 5 lambchops yesterday , I love lamb !

Have the reported non-USA ECM updates previously reported actually been updates or resetting?

Team, since this is a translation from japanese ( unless someone from japan is reading this and can explain it better ) i am guessing that this is a suggestion from a dealer who has not actually tried this and not a confirmed repair, the real cure is actually a software update a la wisedrum, as we all know the older and newer ecu's don't have this problem, only SOME 2014 models have it and then usually after some time of use.

Pretty sure the problem ( if it was a software boo boo ) has been found and corrected, pretty sure the same throttle body and iacv have been in use for a lot of models and over some years, Honda re-uses the same parts on different model bikes, one of the reasons they are in groups of two ( vfr series ) and they just get combined with different configurations at the ends.

Since we are only talking less than 100 bikes worldwide it does not even register to find a fix for a problem that has hardly reached head office in Japan, so unless you happen to know someone in a position to help you the conveyor just keeps going.
There is a well documented case of ac stators failing and overloading the regulator on mostly cb1000 models and they eventually replaced a good number of them under warranty because of the numerous complaints but that was a catastrophic failure and a safety hazard, the bike would unexpectedly stop wherever.

Pekingduck might chime in and see if i'm on the right track here

We don't even have a handle on whether the affected bikes are from the leftovers or not, could be a clue there, is it worth swapping ecu's? maybe but isn't it cheaper to get a new iacv?.

So Eric"o", wisedrum and Pdedse have had the closest comms with the dealership with success and provided very useful feedback to us, as far as i can tell, the rest just repaired it for a low price and got on with it, i bet the number of failed water pumps is far greater than our little gizmo stopping to function properly, at least we can see it coming and get home etc.

Quite possibly Mr Guhl could figure out the difference between the ecu's but it's a lot of work to compare notes for just a couple of ecu's so from a business standpoint not worth the effort, not sure if he writes the entire eeprom content or just some part that may be upgradable, probably worth asking the right type of question to him though.......

From Lambchops translation, seems like the clutch pull in sensor have something to do with corrupting the data in ECU. As far as I remember, most owner with this problem normally have the symptom after certain pro-long heavy traffic ride, which involve a lots of clutch pull and release. So for those who had the problem intermittently, maybe can start testing by pressing and releasing clutch to see if it trigger the symptom. And how many times before the problem started. This way we have at least a proper way to trigger the symptom instead of the problem happen randomly and everything being ok when we reach dealer place.

(07-02-2020, 06:40 AM)Cormanus_imp Wrote: [ -> ]Thanks Lambchops. So, is “resetting” the ECU a job for a dealer or is there another way?

The dealer bulletin reported that:
"・if the idling speed may not drop. Reset the ECU (re-learn idling) to return the idling to the proper speed."

Whereas

"・If the idling speed is lower than the specified value, initialization is performed instead of ECU learning."


I am not sure what "initialization" means.


From what I read, it is a dealer job that requires the HONDA MCS.

The general consensus and feedback from Japanese owners who have had their ECU "reset" is positive and they reported no more issues after.


Here's a link to another post from a Honda shop mechanic that recommends the procedure. Google translate will work sufficiently:
https://nozawakojo.exblog.jp/25836856/


Just to help with translating the text on the Honda MCS tool.

In the third picture, the table shows that an ECU update 3 is available
The final picture below simply says "Updating control module, please do not turn off the ignition. Do not remove the battery"

Lambchops i am happy to say i was wrong with most of my previous post, this looks like the real deal.

Thanks very much for the link and your hard work, it does point in the right direction.
The webpage is in japanese so i copied and paste all the relevant descriptions in google translate and here are the results with regard to the cb1100 reset.
Mcs means; Honda "Motorcycle Communication System"
ecu means; "Engine Control Unit"
pgm-fi means; "Programmed Fuel Injection" system ( Honda proprietary name )

I think it may be a good idea if wisedrum could copy these pictures and show them to his dealer to compare if they are the same.

FROM THE WEBPAGE;

CB1100 ECUアップデート

こんにちは。
Ｍ岡です。004.gif

means;
CB1100 ECU update
It's a sequel.
Hello.
This is Moka. 004.gif


CB1100 ECU update
I was informed that "I will stall if low speed driving continues in a traffic jam".

( max; connecting ecu to cb1100 with battery and pc cable connected ( to k line 0 to 12v serial bi-directional data stream ) )



ＣＢ１１００　ＥＣＵアップデート
「渋滞中の低速走行が続くとエンストする」とご相談いただきました。
アイドリング付近の回転で、発進・停止を繰り返すとＥＣＵの指示と、
ＩＡＣＶの作動にアンマッチが起こるようです！
アンマッチ発生時、IACVが徐々に閉じる方向へ作動し、供給空気が不足した状態になりエンストに至る場合があるようです。
対策のため、ＥＣＵのプログラムを書き換えします！
CB1100 ECUアップデート_e0114857_10273581.jpg

Means;
When starting and stopping are repeated with rotation near idling, the instruction from the ECU
There seems to be an unmatch in the operation of IACV!
It seems that when an unmatch occurs, the IACV gradually operates in the closing direction, causing a shortage of supply air and leading to an engine stall.
As a countermeasure, rewrite the ECU program!
CB1100 ECU Update_e0114857_10273581.jpg

( max; "connecting to ecu and retrieving software version" )


( max; software and vin nr found with option to update to later version )


( max; ecu update in progress. )



「Ｋ様」これで、暫く様子を見てみましょう。

means;
"K-sama" Let's take a look at this for a while.

THE END.

Maybe an affected owner could present these pictures to his dealer and point him in the right direction?

From the update picture it appears the software upgrade is number; 38770-mcg -d43 -M1.rwf

Hope this helps to evolve our quest for the solution. ones and zero's to the rescue.