[marcelsouza]

I am getting FI with 26 blinks and i suspect the problem is "Open or short circuit in left knock sensor"
How do I get there to check if wire is damaged or if the sensor is loose or poorly connected ?
Any help will be highly appreciated .

 

[Richard Clem]

The wire runs from the sensor on the exhaust to the ECM. I think the prescribed test is to switch the wires and see if the error code changes to the other side. If it stays the same, then you likely have an ECM going out.

Richard

 

[techdude2000]

I am getting FI with 26 blinks and i suspect the problem is "Open or short circuit in left knock sensor"
How do I get there to check if wire is damaged or if the sensor is loose or poorly connected ?
Any help will be highly appreciated .

Welcome to the board. The knock sensors are mounted in the bottom of each cylinder bank. They are hidden by the exhaust header on each side. The wire just plugs into it. Chances are it’s a bad ECM. Typically, you need to pull both out and reinstall them swapping sides, then ride the bike again until it throws the code again. If the code changes to 25, then it’s a bad knock sensor. If the code repeats the 26, then it’s probably your ECM going bad. Once you unplug a knock sensor and the ECM, you can take an ohmmeter and check the continuity of the wire up to the ECM’s connector as well as checking it for a short to the shield. The wires are almost never the issue with this code, but it’s always possible to have a loose connection or corrosion at the sensor’s connector.

 

[marcelsouza]

Thank you very much.

 

[Len]

Last week I had a friend come in with a FI code 26. He said the bike wouldn’t idle and ran poorly. We swapped the sensors and the code did not change. Thinking we had a bad ECM or bad wiring between the ECM and the sensor, we removed the shelter and tested the wiring. We couldn’t find any problem with the wiring. Since we didn’t have a replacement ECM, we cleaned all the connectors and reinstalled the original ECM. The bike started and idled perfectly. After a hundred miles, the owner reports no problems.

 

[techdude2000]

Last week I had a friend come in with a FI code 26. He said the bike wouldn’t idle and ran poorly. We swapped the sensors and the code did not change. Thinking we had a bad ECM or bad wiring between the ECM and the sensor, we removed the shelter and tested the wiring. We couldn’t find any problem with the wiring. Since we didn’t have a replacement ECM, we cleaned all the connectors and reinstalled the original ECM. The bike started and idled perfectly. After a hundred miles, the owner reports no problems.

Possible bad connection at the ECM connectors. The knock sensor signal is a very small signal. Hopefully, it’s not a fluke. Normally, even a bad connection on the knock sensors won’t cause an idle or running problem.

 

[marcelsouza]

Update:

Yesterday, I unplugged and cleaned both connectors, then I pulled both knock sensors out, cleaned them, and reinstalled them swapping sides. Rode 60 miles this morning. Bike is running well and I did not get any code . GL1800 2001 with 71,000 miles.

 

[GoldWingrGreg]

I am getting FI with 26 blinks and i suspect the problem is "Open or short circuit in left knock sensor"
How do I get there to check if wire is damaged or if the sensor is loose or poorly connected ?
Any help will be highly appreciated .

For the best help, year is all most always needed !!!

Follow Robs advise about pulling the code. For future testing, be sure to clear or erase the code too.

As for swapping the sensors. I always pull the lower center cowl, and the right front exhaust shield. Doing that should give you access to both. The socket size for the knock sensors are a 24mm. However, and I cannot remember, but either a 15/16" or 7/8" deep socket works well too.

 

[techdude2000]

Update:

Yesterday, I unplugged and cleaned both connectors, then I pulled both knock sensors out, cleaned them, and reinstalled them swapping sides. Rode 60 miles this morning. Bike is running well and I did not get any code . GL1800 2001 with 71,000 miles.

Great! Maybe it was just a connection issue. For future reference, the knock sensor is just a crystal mounted in a housing with wires attached to it. When pre ignition knock occurs, the vibration created by the knock vibrates the crystal and it develops an electrical signal telling the ECM to retard the timing on the side that detected the knock until the signal goes away. Normally, a bad sensor will fail to generate the signal when knocking occurs and the ECM doesn’t know it needs to retard the timing. The other way one can fail is to send out a signal when no knock is actually occurring and this will throw a code. This causes a code because the ECM tries to retard the timing but can’t retard it enough to stop the signal. My guess is a bad connection could generate electrical noise in the circuit and tricks the ECM into “thinking” it needs to retard the timing. Keep us posted if the code returns, :grin2:

 

[Capt. Bob]

I did all the above stuff except swapping the sensors when my '01 started doing the same thing. It ran perfect for a spell then stated acting up again. I didn't swap the sensors because like techdude says the sensors wont cause a bad running condition. I wound up getting a used ECM from a guy on the forum and all was good after that. Good luck with your problem.

 

[marcelsouza]

Thank you. I certainly will if the code returns.

 

[marcelsouza]

Thank you for sharing that information.:smile2: I will update if the code returns.

 

[marcelsouza]

Thank you.

 

[GoldWingrGreg]

When pre ignition knock occurs, the vibration created by the knock vibrates the crystal and it develops an electrical signal telling the ECM to retard the timing on the side that detected the knock until the signal goes away

I had to look that up and am not able to confirm. However, my bet would be that either knock sensor would retard the ignition to all spark plugs, and not to an individual head. If the timing was retarded causing the explosion in the combustion chambers on one side, I'm sure that would cause for a rough running engine. It would certainly not have smooth acceleration.

In Honda's Common Service Manual, there is nothing to indicate if 3 or all 6 spark plugs are affected.