Replacing the Engine Sub-Harness

bstig60

bstig60

Joined
Nov 4, 2018
Messages
830
Age
79
Location
Sharpes, Florida , formally, Nevada City, CA
Bike
GL1800, ST1300
I finally got around to pulling off the right side plastics to investigate the FI code 26 issue while my bike is down to have the riders seat modified. When I pulled off the plastic, I found that there had been a "half a$$" repair done. The wire running to the knock sensor had been spliced and the cap for the wire to connect to the sensor is gone. A bare connector was attached to the new wire and silicone used to close the hole on the knock sensor to protect the connection from the elements.
I have a new Engine sub harness and knock sensor that came with the bike. Easy enough to replace the knock sensor, but since the existing engine sub harness has been modified, I would like to replace it with the new one I have. In searching the service manual I have online, I don't find anything that refers to replacing the sub harness, so I would like to know if anyone has done this and exactly what is involved.......
 

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I've replaced that harness on my 2005 ABS. It's a bit of a PITA as you will need to remove the air cleaner and probably the throttle bodies to reach all the connectors. The harness connects to both the left and right knock sensors so before pulling the disconnected plug from the left sensor, tie a line to it you can used to pull the new one back through. It also connects to the oil pressure switch and the thermostat housing down in the V of the engine. There's a ground connections on the right side of the crank case too.
 
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Good luck, I would certainly try to repair the harness first if you can access the damaged bit without removing it.
 
I just replaced mine a few days ago. You'll need to pull the Tupperware, upper tank, air cleaner, throttle bodies in order to route the harness and reach the EOP switch and ground wire on the thermostat. Unfortunately it is a big job, so I would consider replacing the water lines like I did while I was in there. You can see some of my pics here in this thread. https://www.st-owners.com/forums/threads/alternator-core-failure.166684/page-5
 
I also attempted to replace the harness. Rather than pulling everything, I ran the harness to the areas I could reach and spliced the rest. The section of the harness to the knock sensors remained in tack. I also replaced the sensors. However, this did not resolve the issue. In the end I replaced the ECM with a used one from a later model. Have had no issues since.
 
Replaced mine on the P bike a while back. It can be done without removing the throttle bodies if the radiator is removed and there are a second set of hands available. Plastics, tank and air filter housing do need to be removed though. Tying strings to the existing harness ends before removal is imperative for routing and access. With the throttle bodies in place upper forward connections are not visual from above but can be accessed, and with the radiator and I believe the thermostat housing removed, guidance from the front of the bike makes things possible. Pick you poison. if you are comfortable with TB removal and don’t have a second set of hands things will be easier going that route. If not, try my suggestion. Minimally do tighten all your hose clamps while you’re in that far.
 
Checked the wiring and it was good to the ECM on both knock sensors.... Found a used ECM on Ebay from an '03 bike. Bougth it for $60 bucks with free shipping.. Installed it and have put about 100 miles on the bike since and no FI light. Hopefully, it lasts....
 
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