FI Code 26

Redfish I'm glad you can get back to enjoying your bike. I remember somebody posting that the mechanic at the dealership told him that 9 times out of 10 it is the ECU. Looks like he is right based on your experience and some of the other threads on knock sensor codes.

Since I was just reading another thread on this very issue I thought I would give this thread a bump and an update. I have had zero issues with the ECU. I have not seen any FI codes. The bike is running beautifully and it has been getting a (very) few miles.

I'm a little confused here. I've seen posts on this forum and a "Manual correction" posted in ST-Wiki that suggest the Honda SM has the knock sensors associated with the failure codes 25 & 26 reversed. However, someone who unplugged a sensor lead to see which code was displayed verified the manual is correct in that respect, although one or two of the troubleshooting procedures and the wire colors described in the manual are apparently incorrect. https://www.st-owners.com/forums/showthread.php?43161-FI-Issues-(Code-25)/page2
Wire colors should be easy enough to check - the wire at the sensor should be color coded the same as the wire at the ECM connector, unless a color coding switcheroo occurs at the 10-pin connector between the lower sub harness andthe harness connected to the ECM.
I would like to be able to troubleshoot and correct the problem by removing tupperware from just one side, so it would be nice to know which side before I start.

Don, in my case they were not reversed. The Service Manual was just wrong. It listed the right side as Red/Blue and the left side as Blue. In fact, the right side was Black, the left side was Red/Blue. My '04 wiring matched the section for "'07 and later".

You are correct about the wire color being the same at both ends. Here is why I did not pick up on it: 1) I was trusting the expensive Genuine Honda Service Manual. 2) Since all my forum research said it was heat killing the connector I assumed that the original Red/Blue wire insulation had been blackened by heat. I see that a great deal at my job.

You cannot imagine my disgust and anger when I found the service manual was wrong. Blind trust instead of pure troubleshooting. I should have known better.

What year is your ST? And where the heck is Alief, TX? (I'll Google that) My suggestion would be to find someone close who is willing to swap ECUs for a few minutes. The ECU# changes after '07 and the plugs are not compatible with earlier years.

Don B said:

I'm a little confused here. I've seen posts on this forum and a "Manual correction" posted in ST-Wiki that suggest the Honda SM has the knock sensors associated with the failure codes 25 & 26 reversed. However, someone who unplugged a sensor lead to see which code was displayed verified the manual is correct in that respect, although one or two of the troubleshooting procedures and the wire colors described in the manual are apparently incorrect.

Click to expand...

I wrote that, so I'll take care of correcting it if it's wrong.

What we should check is whether there's a difference between editions of the manual, because they may have corrected it at some point. I have two copies, one for the 2003 model dated June, 2002 and one for the 2003-2004 dated March, 2004. Both list 25 for the left and 26 for the right and the wiring diagram numbers the sensors 1 and 2 without saying which side they go on. The wiring diagram in the 2003 edition is inconsistent (see attached); it looks like the placement of the color codes was offset to the right a bit, which is easy to miss if you're not looking for it. This was corrected in the 2004 edition.

If anyone's got newer versions than mine, I'd like to know if the table in chapter 5 was changed or not.

--Mark

My manual was issued May 2010. I never looked at that diagram, I followed the FI Troubleshooting procedure. There are two sections for troubleshooting the FI, 1) '03 to '07 and 2) After '07. My bike is an '04 so naturally I went by that section. I flipped to the "After '07" section by accident and decided to check that. Those wire colors match what I have on my '04. My manual also is incorrect with the troubleshooting procedure in the "After '07" section but at least the wire colors are correct.

Code 25 is the left sensor and the wire is Red/Blue.
Code 26 is the right sensor and the wire is Black.

The only diagram I found in my chapter 5 is the system diagram and it is much different from what you pictured. It is also not nearly as useful. It is on page 5-7, if there is another wiring diagram in that chapter I have not found it. Tell me where to look and I will try again.

Redfish said:

What year is your ST? And where the heck is Alief, TX? (I'll Google that) My suggestion would be to find someone close who is willing to swap ECUs for a few minutes. The ECU# changes after '07 and the plugs are not compatible with earlier years.

Click to expand...

Redfish, my ST is a 2003, the one with the faST black wheels. If you Google Alief and follow the Wikipedia link, you'll find out where Alief is. It's mostly within the Houston city limits. My street address is actually a Houston address, but the post office where I get most of my snail mail is the Alief PO. The city of Bellaire is similar, except it is entirely within the Houston city limits.
Anyway, I'm optimistic that my problem may just be bad gas - I mean the ST problem, that is. I've had the bike less than 7 years now, and never had a reason to even look for the FI service connector until today. Had to extract the owner's manual from under the rear seat and remove the tool kit to look for it, later discovered I wouldn't have had to do the latter if I had known where the connector was. Anyway, I first tried the procedure in the manual to display the trouble code, but it did not display any code. I suspected that in advance, since the FI light hadn't lit up since I filled it with gas yesterday afternoon. Next I tried to persuade it to display the code 26 by starting it, let it idle until the coolant temp displayed 1 bar, then revved it up to 4k and held it there for 15-20 seconds. No error code displayed. I'm hoping the FI light yesterday was just a glitch, since I haven't yet figured out where the ECM is located... I did find the ABS control module, however.
Don

Don, the ABS module and the ECU are together at the rear of the bike, in front of the tail light. It is accessible just by removing the seats.

I hope it is just bad gas. If you read this thread from the start (Yes, I know it gets long and boring!) you will see that mine was intermittent to begin with and steadily got more frequent. You can only read the code with the kickstand technique if the FI light is illuminated already. I never used the connector to display the code, I just used the kickstand.

I had already looked up Alief Texas by the way. My first thought was to make arrangements to meet in the middle and swap ECUs for a brief test. Then I remembered the lower speeds vs. reduced fuel economy of the FI code.

If I can answer anything else or help you in any way, don't hesitate. Again, I hope you had bad gas. (Not YOU! Your motorcycle.) I would be surprised though.

For what it is worth my code 25 was the left knock sensor and In my case it apparently was just a poor connection. I checked continuity from knock sensor plug to sub harness plug = good then from sub harness plug to ECU plug, also good. I did two things one of which might have solved the problem 1st I noticed the knock sensor wire at the knock sensor had very little slack in it. I was able to give it a little bit of slack by pulling on the wire a little were it disappears near the frame. Then I put dialectic grease on every pin connector on the sub harness and the ECU ( not just the knock sensor pins) I also put some on the knock sensor pin itself before reconnecting the plug. It has been several months now with no light.


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Redfish said:

Don, the ABS module and the ECU are together at the rear of the bike, in front of the tail light. It is accessible just by removing the seats.

I hope it is just bad gas. If you read this thread from the start (Yes, I know it gets long and boring!) you will see that mine was intermittent to begin with and steadily got more frequent. You can only read the code with the kickstand technique if the FI light is illuminated already. I never used the connector to display the code, I just used the kickstand.

I had already looked up Alief Texas by the way. My first thought was to make arrangements to meet in the middle and swap ECUs for a brief test. Then I remembered the lower speeds vs. reduced fuel economy of the FI code.

If I can answer anything else or help you in any way, don't hesitate. Again, I hope you had bad gas. (Not YOU! Your motorcycle.) I would be surprised though.

Click to expand...

Redfish, apparently my code 26 was not the result of bad gas after all, since the MIL displayed the code several times over the 3 months following the first occurrence back in February. I never noticed a change in the bike's performance on any of these occasions, and the fuel consumption was not affected. I haven't done any trouble shooting yet, since the problem rarely occurs for me. Most of my riding so far this year has been in or near the Houston metropolitan area, so I rarely exceed 4k rpm for 10 sec or longer.
Now for a new twist: a few days ago, the MIL lit up again and when I checked the failure code it no longer displayed code 26. It now displays code 25 (LEFT knock sensor). I've observed it several times during the past few days by running the bike up to 4k or more in 2nd gear (or while parked) and I get the same code every time. I've watched it repeat the code for several cycles, looking for 26 to lite up again, but that doesn't happen. This makes me strongly suspect a faulty ECM, but I will check the connectors and continuity and insulation from both sensors to the 10-pin connector before I go to the ECM plug to check the sensors wiring all the way to the ECM. Unfortunately, I can't access the ECM by removing the rear seat on my '03, I'll have to follow the shop manual procedure and remove the rear cowl to access it. I need to ask how you went about checking the voltage output of the knock sensors. Can I unplug the sub harness from the 10-pin connector and measure the voltages at the plug, or will the bike start and run with it unplugged? Knowing what I've got going to the ECM will help a lot trying to trouble shoot the problem. Thanks,
Don

The fact that the error code has switched sides makes me strongly suspect the ECU. Ah, but troubleshooting this...

The reason I was able to read the voltage coming from the knock sensors to the ECU was because I had already cut the wires about 6 inches from the gang plug at the ECU. Therefore, I had a handy butt splice I could put the meter lead into. That was a result of being led astray by the misinformation in the Honda Service Manual.

I am not sure about the sub harness but I know that if the big plug is not plugged into the ECU the bike will not start.

My thoughts here... IF I were doing the troubleshooting, I would have 3 options. You may come up with others, they may be better.

1. Borrow someone else's ECU. Quickest and easiest.

2. If you have a service manual and can verify which color wires go to which sensor, (this would mean removing both lower fairings) you can:
A) Disconnect both sensors. Insert a wire into each female plug with a female spade connector on the free end. Criscross the wires under the bike and connect the female spades to the knock sensors. This effectively "swaps" the left and right sensors. Rev the bike up to 4K for 10 seconds and see what code you get.
OR
B) Cut each of the sensor wires about 6 to 8 inches away from the ECU gang plug. Using wire nuts (because they are temporary) criscross the two wires and reconnect them. Rev the bike up to 4k for 10 seconds and see what code you get.
OR
C) Make a VERY SMALL nick in the insulation of each wire, just enough to get the point of your meter probe to touch the metal wire strands. Read the voltage from each one. When you are done, a couple wraps of electrical tape over the removed insulation and you are good as new.

None of this will be fun or easy. If I have not explained this properly, PM me. Or, I will be watching this thread. If necessary we can swap phone #'s and perhaps I can explain better over the phone.

Good luck, let me know how I can help you.

Redfish, I saw the following in one of your posts on another forum:

The Honda part # for '03-'07 should be 38770-MCS-L01
Edit: My ECU has two #s. The # I listed above and 9725-104020

One of the photos in the following ebay ad for a 2003 ST1300 ECM shows the same part number indicated above, but the "other number" was different. Would that be the unit's serial number (see attachment)? There's only one day left to bid, but I don't plan to jump on it since I haven't yet determined positively that the ECM is my problem, and don't want to buy a replacement "just in case".

http://www.ebay.com/itm/03-Honda-ST1300-1300-FUEL-INJECTION-COMPUTER-ECU-ECM-/131214356407?pt=Motorcycles_Parts_Accessories&hash=item1e8cfc2fb7

Don B said:

Edit: My ECU has two #s. The # I listed above and 9725-104020

Click to expand...

The only number you care about is the Honda part number. If it's 38770-MCS-L01, it's good in any bike through 2007.

--Mark

Redfish said:

Code 26......

...I had already installed two excellent test points at the ECU plug in the form of two butt splices. I connected my meter and started the bike.

I found that both the right and left knock sensors generated about -114.5 millivolts with the bike idling. Both generated about -122 millivolts at 4100 RPM. No appreciable difference between right and left sensor. No spiking, no dropping, no PROBLEMS!....

Click to expand...

Hi Redfish,

I'm experience something very similar. It started with code 26, then the last time I check, it was 25. Not sure why it changed. I've tested both side's wire for short and continuity and they were fine. Igofar suggested cleaning the 5 way T under the tank. I found it to be clean and no debris blocking the T.

My next step would be to verify the code, then switch the wires between left and right to see if the code change. That will at least tell me if the error is caused by the sensor.

Can you elaborate the procedure to test the sensors with a multimeter? Is the done with all the wires in place and you just tap into the wire to take the reading? Or is it done with the wires unplugged?

Thanks
JC

Hey I was looking at your post about the code 26. I to had the same problem on my 2003 ST1300 with right knock sensor wire crumbling though the wire was fine and wrapped it in flame retardant tape and changed the sensor also. Ended up having to replace the ECM. Hard to find a used one as I have looked for many months and if I did they wanted like $400.00 used "screw that"

Getting the 25 on my 03, but no power loss of mileage drop.

Any downside to just ignore it?

Well, there's this:



--Mark

Blrfl said:

Well, there's this:



--Mark

Click to expand...

Is timing adjusted independently on each bank?

MidLife said:

Is timing adjusted independently on each bank?

Click to expand...

It's all done in software, and I have no special insight into the ECM firmware. The hardware's certainly there to do it, but the ST's FI system was born at a time that straddled primitive implementations and things becoming more sophisticated. The two sensors could be there because each is better at hearing what's happening on their own side of the engine or because Honda considered controlling ignition timing important enough to build in some redundancy. In either case, the ECM does everything it can to avoid knocking as a way to prevent engine damage, so why stymie it?

The more practical end of it is that if you ride around with the FI light on, that's going to become the new normal. If the other sensor (or something else) fails and that part of the system has to start running open-loop, you're not going to notice unless you make a regular thing of checking the fault codes.

--Mark

Blrfl said:

It's all done in software, and I have no special insight into the ECM firmware. The hardware's certainly there to do it, but the ST's FI system was born at a time that straddled primitive implementations and things becoming more sophisticated. The two sensors could be there because each is better at hearing what's happening on their own side of the engine or because Honda considered controlling ignition timing important enough to build in some redundancy. In either case, the ECM does everything it can to avoid knocking as a way to prevent engine damage, so why stymie it?

The more practical end of it is that if you ride around with the FI light on, that's going to become the new normal. If the other sensor (or something else) fails and that part of the system has to start running open-loop, you're not going to notice unless you make a regular thing of checking the fault codes.

--Mark

Click to expand...

Thanks for the insight!

If falling back to open-loop mode, power and mileage drop should be noticeable, right?

Didn't have to trigger the code read: It flashed on its own on the following start up. Not sure when it is that you have to use the jumper to trigger the codes.

Lately MIL hasn't blinked 25 on start up anymore. It goes off normally on restart and doesn't come back on until sustained highway speed.

Manual says 25 is left, but from posts, looks like for a 2003 it could be in fact the right sensor? Wouldn't be surprised to find issues with wires/insulation on the right rather than left, as it runs hotter on the right.

Thanks again for the help.