Fault code 26

ASPC

ASPC

Joined
Jul 3, 2021
Messages
714
Location
Louisiana
Bike
07 ST1300 ABS
Last night while riding in hot weather the bike gave fault code 26. So I read about it here and went and cleaned the five way t connector under the tank. It was not completely blocked but one port was very restricted. After reassembly and reseting the computer the engine seems a lot smoother and I now wonder what all those little pipes do. Do they effect fuel and ignition timing?

I also noticed at the time of the fault code that the bike was running a lot hotter than normal and seemed to lack power and surge a little.

I don’t know if the problem has been solved yet but the engine now sounds very nice, smooth and zippy up to 8K while on the stand. Will ride it later when its cooled down to around. 90 degrees.

The bike’s got premium fuel with up to 10% ethanol in it at the moment. I don’t like that and wonder if that has anything to do with this issue in hot weather.
 
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The bike will run fine on 91 octane. Many guys have said regular is ok, but I doubt your problem is the gas. Did the fault code go away? What is the year? Your rough running and low power are symptoms of a clogged 5 way T.
 
ASPC said:
Last night while riding in hot weather the bike gave fault code 26. So I read about it here and went and cleaned the five way t connector under the tank. It was not completely blocked but one port was very restricted. After reassembly and reseting the computer the engine seems a lot smoother and I now wonder what all those little pipes do. Do they effect fuel and ignition timing?

I also noticed at the time of the fault code that the bike was running a lot hotter than normal and seemed to lack power and surge a little.

I don’t know if the problem has been solved yet but the engine now sounds very nice, smooth and zippy up to 8K while on the stand. Will ride it later when its cooled down to around. 90 degrees.

The bike’s got premium fuel with up to 10% ethanol in it at the moment. I don’t like that and wonder if that has anything to do with this issue in hot weather.
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I am also curious about the need for the little pipes.
 
Those are the vacuum lines. The component regulates the fuel flow in the system. Did you do the throttle body sync while you had it opened up?

Error 26 is typically the ECU has failed. What year is your bike?
 
SMSW said:
The bike will run fine on 91 octane. Many guys have said regular is ok, but I doubt your problem is the gas. Did the
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SMSW said:
The bike will run fine on 91 octane. Many guys have said regular is ok, but I doubt your problem is the gas. Did the fault code go away? What is the year? Your rough running and low power are symptoms of a clogged 5 way T.
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no it’s still there.
 
aniwack said:
Those are the vacuum lines. The component regulates the fuel flow in the system. Did you do the throttle body sync while you had it opened up?

Error 26 is typically the ECU has failed. What year is your bike?
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2007
 
Code 26 is still there and it backfired under deceleration. Next I’m going to check the wiring and change the plugs.
 
When was the last time it had heavy maintenance? For an 07, it sounds like it's time to swap out the hoses and fluids, change the thermostat, and get the throttle body sync done.
 
I believe code 26 means the ECU is gone. The only cure is replacement with a used one. BUT, I'm not sure about this, I am sure more knowledgeable guys will chime in.

Oops, @aniwack said that above. There have been a few threads describing this problem - you can search for them in the search box - top of this page right end of blue bar. I seem to remember someone found used police ecu's for much cheaper than an OEM one. Honda made changes in '08, so you have more model years to choose from.

Ignition timing is controlled by the ECU. If you use low octane gas that knocks, the knock sensor tells the ECU to retard the timing.
 
SMSW said:
I believe code 26 means the ECU is gone. The only cure is replacement with a used one. BUT, I'm not sure about this, I am sure more knowledgeable guys will chime in.

Oops, @aniwack said that above. There have been a few threads describing this problem - you can search for them in the search box - top of this page right end of blue bar. I seem to remember someone found used police ecu's for much cheaper than an OEM one. Honda made changes in '08, so you have more model years to choose from.

Ignition timing is controlled by the ECU. If you use low octane gas that knocks, the knock sensor tells the ECU to retard the timing.
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Code 26 is a knock sensor issue. If anything on the engine is knocking the knock sensor will detect it.
 
ASPC said:
Code 26 is a knock sensor issue. If anything on the engine is knocking the knock sensor will detect it.
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In five years I've yet to have a Code 25/26 be the actual sensor.

SMSW said:
Ignition timing is controlled by the ECU. If you use low octane gas that knocks, the knock sensor tells the ECU to retard the timing.
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I run 87 E0 or 93 E10. No performance issues in five years.
 
Changed the oil, went down the road super smooth and quiet. Opened it up and there was a power drop around 5K and the FI light came on. But it doesn’t stay on when I turn it on and off. This coincides with a new tank of fuel.
 
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Check the knock sensor wiring all the way back to the ECU. The knock sensor wiring on the left side of the bike runs too close to the exhaust and gets burned due to high heat. In my case, after checking out the knock sensors and wiring as mentioned above, I was lucky enough to find a cheap ECU on eBay and so far. that has solved the problem.
 
I’ve noticed the fuel pump which is usually loud when the ignition is first turned on is now very quiet and muted and I wonder if the reason for the code 26 is fuel starvation due to a blocked filter. This could also explain the idle issue and the surging.
 
ASPC said:
Changed the oil, went down the road super smooth and quiet. Opened it up and there was a power drop around 5K and the FI light came on. But it doesn’t stay on when I turn it on and off. This coincides with a new tank of fuel.
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One of the symptoms of a bad ECU is that the FI light comes on and the power drops when you rev it above 4k. You can run it all day with no problem if you keep it below 4k. You will also find that your gas mileage drops way off once the light comes on.

When I had this problem, the fuel and oil didn't make any difference. It was all about the revs. I tried a used ECU with no luck; a new ECU fixed the problem.
 
Wondering if I can temporarily disconnect the knock sensors to remove that part of the problem.68F6D606-8C6E-45E2-A134-8FCA3809F58A.jpeg
 
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ASPC said:
Changed the oil, went down the road super smooth and quiet. Opened it up and there was a power drop around 5K and the FI light came on. But it doesn’t stay on when I turn it on and off. This coincides with a new tank of fuel.
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ECU failed.

IT IS NOT THE KNOCK SENSOR.
 
Disconnecting the knock sensors will have the same effect as having a defective knock sensor. The ECM will not see the voltage from the knock sensor that it is expecting. It doesn't know if this is due to a defective knock sensor or a disconnected knock sensor, and will react the same way.

The best that you can do is swap the knock sensors from side to side to see if the fault code changes, check all of the wiring for damage, shorts, continuity, etc., all the way back to the ECM. If that all checks out, the ECM is the last man standing unfortunately.
 
I’m assuming that everyone who replaced the ECU did it themselves rather than have someone else do it?
 
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