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Old September 28th, 2013   #1
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Join Date: Mar 2011
Location: Prairieville, Louisiana
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Default FI Code 26

Code 26. Two long blinks followed by 6 short blinks. Right Knock Sensor.

Well, maybe. I originally piggybacked this onto another thread but now I think my story deserves its own thread. No, all stories don't have happy endings.

Running the engine above 3900 RPM for 10 seconds will generate this fault code. Instantly power is cut, and fuel mileage plummets. 3900 RPM looks like 72 mph on the speedometer. It is 68 mph on the GPS. This fault will give you 37 mpg at 73-74 GPS mph on the Interstate.

First, if the red FI light in the dash comes on you must read the code. Reading the code is very simple. If you know how. Engine running, FI light on, bike in neutral, lower the kickstand. Then count the blinks. A long blink (1.3 seconds) counts as 10. In my case two long followed by 6 short equals 26.

Your Genuine Honda Service Manual will have a chart telling you what the # of blinks translates into. My bike is an '04 so this is found on pages 5-14 thru 5-16.

A quick and desperate check of this ST forum told me that most often the problem was not the sensor. It is the plug and or wiring breaking down from the intense heat of its location. Cutting off the plug and replacing with a suitable spade connector solved almost everyone's issues.

I removed all the Tupperware from the right side. I unplugged the knock sensor. It is inconveniently located between the exhaust header pipes and the engine block. I checked the plug and it looked fine.

The troubleshooting section of the Honda Service Manual says to check for continuity to ground from the plugs on either end of the wiring harness. Then it says to check for continuity between the two plugs. Basically, you are checking to see if the wire has been damaged and is going to ground or has burned/rubbed/broken in two between the sensor and the ECU. If it is not going to ground and the wire is intact, the problem must be the sensor.

The Honda Manual is WRONG concerning the wire colors for my '04 ST. It clearly states on pages 5-49 and 5-50 that the wire colors are:
Left Sensor Wire-Blue
Right Sensor Wire-Red/Blue
This is not correct for my bike. The manual has two sections for two different year groups. The first is for '03-'07. The second is for '07 and later.
My ST is wired like the '07 and later version. My sensor wires were:
Left Sensor Wire-Red/Blue
Right Sensor Wire-Black

Using the wire colors the manual stated for my year I decided the wire between the sensor and the ECU was bad. I ran a temporary wire and cut/spliced into the wiring harness just ahead of the ECU. Tried running the bike, still got the code. Purely by accident I looked at the section for '07 and later and was able to re-diagnose the wiring.

I wound up removing the left side Tupperware during the confusion phase so I tried running separate wires under the bike to "switch sides" with the sensors. I stuck the stripped ends of #14 wire into the female sensor plugs and used spade connectors to attach the other end of the wires to the sensors. No code. Re-connected the plugs. Got Code. Stuck wires back in, Ran bike. No code. R-connected plugs. Got Code.

Sigh... Plugged left sensor back in. Jammed wire back into female plug on right side and plugged spade connector onto right knock sensor. No code.

Decided the connectors inside the female end were "sprung" out and not making good connection to sensor. I found that the plug (sensor end) was not making a good connection at the sensor. I attempted to use a tiny screwdriver to pry the metal connectors out and...

The plug shattered in my hands. The more I tried to repair, the more the brittle plastic crumbled in my hands. I replaced the plug with a tiny spade connector.

Ran the bike on the centerstand, no code. Fixed it!

Or not...
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