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GL1800 Doctor
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Discussion Starter #1 (Edited)
This is for anyone who either doesn’t have a copy of the ETM or anyone who has a copy and can’t find this information in it.

The GL1800 has a junction connector that can get bad connections in it and cause the FI system to malfunction along with a few other systems that share the junction. If you are having issues with the way the bike is running at idle or at any other speed, you should investigate the power coming to the ECM on the black/yellow wires. If the power is more than a volt below the battery power, then you should inspect this junction connector for heating(browning on the sides, discoloration of the pins), and corrosion inside of its cap. It is blue and resides in the main harness bundle just in front of the relay bank under the seat. Some bikes will have it wrapped up in the harness tape and others may have it hanging out of the harness. It has two different names based on which model year of wing you have. On the 01-05 models it is called C5. On the 06-08 models it’s called C25. It was upgraded after the 08 model year and doesn’t develop the issues we see with the first 8 years of production. Below is a list of the pins and wires related to the model years and systems affected:

01-05 Models
C5
Pins 1-6 Accessory Circuit lightgreen/black wires
Pins 7-10 Fuel System Power black/yellow wires
Pins 11-16 Cruise Ctrl Power black/yellow wires
Pins 17-20 Tail light Power brown/white

06-08 Models
C25
Pins 1-6 Cruise Ctrl Power black/yellow wires
Pins 7-10 Tail light Power brown/white wires
Pins 11-16 Accessory Circuit light green/black wires
Pins 17-20 Fuel System Power black/yellow

Take note that the cruise control power and the FI system wires are the same colors, but they are not connected to each other.
 

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This is for anyone who either doesn’t have a copy of the ETM or anyone who has a copy and can’t find this information in it.

The GL1800 has a junction connector that can get bad connections in it and cause the FI system to malfunction along with a few other systems that share the junction. If you are having issues with the way the bike is running at idle or at any other speed, you should investigate the power coming to the ECM on the black/yellow wires. If the power is more than a volt below the battery power, then you should inspect this junction connector for heating(browning on the sides, discoloration of the pins), and corrosion inside of its cap. It is blue and resides in the main harness bundle just in front of the relay bank under the seat. Some bikes will have it wrapped up in the harness tape and others may have it hanging out of the harness. It has two different names based on which model year of wing you have. On the 01-05 models it is called C5. On the 06-08 models it’s called C25. It was upgraded after the 08 model year and doesn’t develop the issues we see with the first 8 years of production. Below is a list of the pins and wires related to the model years and systems affected:

01-05 Models
C5
Pins 1-6 Accessory Circuit lightgreen/black wires
Pins 7-10 Fuel System Power black/yellow wires
Pins 11-16 Cruise Ctrl Power black/yellow wires
Pins 17-20 Tail light Power brown/white

06-08 Models
C25
Pins 1-6 Cruise Ctrl Power black/yellow wires
Pins 7-10 Tail light Power brown/white wires
Pins 11-16 Accessory Circuit light green/black wires
Pins 17-20 Fuel System Power black/yellow

Take note that the cruise control power and the FI system wires are the same colors, but they are not connected to each other.
Thanks for taking the time to put this information together TD. I've copied it and placed in a personal folder (to improve my chances of finding it again) for future reference. As usual, your contribution here is very much appreciated!
 

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This problem is common enough and has such odd symptoms that I suggest Rob's post be granted "sticky status" BUT include the diagram provided long ago by Chet, if such is proper etiquette.


prs
 

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GL1800 Doctor
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19,351 Posts
Discussion Starter #5
This problem is common enough and has such odd symptoms that I suggest Rob's post be granted "sticky status" BUT include the diagram provided long ago by Chet, if such is proper etiquette.


prs
I think you are talking about the rear lighting ground issue, that would be a different connector and set of issues. :nerd: Maybe I’ll do a workup on it as well.
 

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Hey Rob,
I have a friend that has an 03 Gl1800 that has been triked with 92,000 miles. He tells me that the bike runs great but as soon as he revs it above 2000 rpm either sitting or riding, the FI light comes on. He can shut it off and the FI light clears, but comes right back on the moment he revs it up again. I have warned him that the electrical system isn't my strong suit but I will see what we can find. He is bringing it for me to look at and perform general maintance (brakes, plugs, filters, etc.) Any suggestions as to what to look for since we know it doesn't have a side stand?
 

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GL1800 Doctor
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19,351 Posts
Discussion Starter #7 (Edited)
Hey Rob,
I have a friend that has an 03 Gl1800 that has been triked with 92,000 miles. He tells me that the bike runs great but as soon as he revs it above 2000 rpm either sitting or riding, the FI light comes on. He can shut it off and the FI light clears, but comes right back on the moment he revs it up again. I have warned him that the electrical system isn't my strong suit but I will see what we can find. He is bringing it for me to look at and perform general maintance (brakes, plugs, filters, etc.) Any suggestions as to what to look for since we know it doesn't have a side stand?
What you will need to do first, is determine if it still has the side stand switch and use it after the FI light comes on to see if you can retrieve the code it’s throwing. If it doesn’t have the switch, you will have to disconnect the wires and reconfigure them to simulate the switch to get the code. Let me know what you find when you get into it. If the switch is still there, start it in neutral, rev it until the light comes on, then move the side stand switch clockwise until the “S” comes on the dash and the FI light should start flashing the code. If the switch is gone and just the wires remain, put it in neutral, disconnect the green wire from the green/white wire, then start it, rev it until the FI light comes on then connect the green wire to the yellow/black wire. The “S” on the dash should light and the FI light should flash the code.
 

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I'm new to the forum, but have read other post and would like to ask "techdude2000" a question. Not sure how to go about it. It has to do with fuel pump, wiring, and relay chatter. I am pretty lost on this site so I do not know where to look to see a response from you. Thank you
 

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I'm new to the forum, but have read other post and would like to ask "techdude2000" a question. Not sure how to go about it. It has to do with fuel pump, wiring, and relay chatter. I am pretty lost on this site so I do not know where to look to see a response from you. Thank you



Easy-peasy. Start a new thread* with your question (preferably in the GL1800 Tech Board section). There are a lot of knowledge folks here, so even if the GL Doctor (techdude) isn't available, someone should be able to point you in the right direction. After you post your question(s), the other folks' replies will show up below it.


*you should see a button with "> Post New Thread" along the left side of your screen just above the top of the list of threads in the section.
 

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GL1800 Doctor
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Discussion Starter #10
I'm new to the forum, but have read other post and would like to ask "techdude2000" a question. Not sure how to go about it. It has to do with fuel pump, wiring, and relay chatter. I am pretty lost on this site so I do not know where to look to see a response from you. Thank you
Sent you a private message.
 

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Attached are a couple photos of two joint connectors located underneath the airbox. One distributes power and the other distributes ground. We have had reports of both of them failing, which usually results in bikes not starting. They provide power and ground to multiple fuel injection sensors and the ECM. If you have an older bike with problems starting this is one area to check. Access is pretty tough, and most times you'll have to pull out the airbox to get to them. The connector colors and look may vary depending on model year. Two examples are shown below.



Power wires are normally black with yellow stripe
Ground wires are green
I believe the three white/blue stripe wires shown in photo below are for the reverse system



See these threads for reference.


https://gl1800riders.com/forums/5-gl1800-tech-board/438345-fuel-pump-relay-chatters.html


https://gl1800riders.com/forums/5-gl1800-tech-board/166156-search-honda-multi-connector-wire-harness.html


Originally Posted by Quickdraw V I think just one circuit caused the majority, if not all, of the problems - that duel circuit cap and it was simply hard to find. The ground cap may have had something to do with it too, but it was repaired before I could inspect it. Too many sensors and safety switches talking to each other to know for sure.

Cause: wear and tear! Those poor connectors suffer a lot of vibration and many heat/cool cycles - especially on top of the engine. We didn't seem to have so many burnt connections when mfgs used bullet connectors. Spade connectors seem to be more susceptible to loosening with heat cycles and vibration. Spade connectors can slide and twist sideways slightly even when they are new and working perfectly. That sliding can create an arc. Once they arc, it's all over in due time. One arc starts a vicious cycle of wear that eventually breaks the connection. (Think of the stator connector that spoiled a lot of GL1200 and Shadow charging systems.) Weather and road chemicals play a part too I think. If deicer gets in a connector - game over. Pressure washing probably doesn't help since water can be forced into places it wouldn't normally get and it can't get out!

That's my dribble on the situation, but I'm certainly open to other ideas.

Maybe(?) if each of those connectors had a squirt of DeOx when new, we wouldn't have quite as many failures.

I did find some photos . . .

The cap after the black/yellow patch was made. Ground Cap repair is in the background.





We also found a pile of mouse collected trash. They hadn't chewed any wires, thankfully!

 

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This is for anyone who either doesn’t have a copy of the ETM or anyone who has a copy and can’t find this information in it.

The GL1800 has a junction connector that can get bad connections in it and cause the FI system to malfunction along with a few other systems that share the junction. If you are having issues with the way the bike is running at idle or at any other speed, you should investigate the power coming to the ECM on the black/yellow wires. If the power is more than a volt below the battery power, then you should inspect this junction connector for heating(browning on the sides, discoloration of the pins), and corrosion inside of its cap. It is blue and resides in the main harness bundle just in front of the relay bank under the seat. Some bikes will have it wrapped up in the harness tape and others may have it hanging out of the harness. It has two different names based on which model year of wing you have. On the 01-05 models it is called C5. On the 06-08 models it’s called C25. It was upgraded after the 08 model year and doesn’t develop the issues we see with the first 8 years of production. Below is a list of the pins and wires related to the model years and systems affected:

01-05 Models
C5
Pins 1-6 Accessory Circuit lightgreen/black wires
Pins 7-10 Fuel System Power black/yellow wires
Pins 11-16 Cruise Ctrl Power black/yellow wires
Pins 17-20 Tail light Power brown/white

06-08 Models
C25
Pins 1-6 Cruise Ctrl Power black/yellow wires
Pins 7-10 Tail light Power brown/white wires
Pins 11-16 Accessory Circuit light green/black wires
Pins 17-20 Fuel System Power black/yellow

Take note that the cruise control power and the FI system wires are the same colors, but they are not connected to each other.
Rob the Black yellow wire at C25 on 08 level 4 go to alternator , does that provide feed back to ecu? I know it provides power to cruise circuit I get a headache looking at wire diagrams... lol
 

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GL1800 Doctor
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Discussion Starter #15
Rob the Black yellow wire at C25 on 08 level 4 go to alternator , does that provide feed back to ecu? I know it provides power to cruise circuit I get a headache looking at wire diagrams... lol
It is providing the turn on power(ignition) to the regulator in the alternator. That’s why the alternator will stop charging the battery if the cruise fuse blows. There is a black wire running between the ECM and the alternator that allows the ECM to control the alternator. This is evident when you first start the engine, the ECM keeps the alternator output off until the engine speed has stabilized for a short period of time.
 

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It is providing the turn on power(ignition) to the regulator in the alternator. That’s why the alternator will stop charging the battery if the cruise fuse blows. There is a black wire running between the ECM and the alternator that allows the ECM to control the alternator. This is evident when you first start the engine, the ECM keeps the alternator output off until the engine speed has stabilized for a short period of time.
Ahhhhh,
That's why my self installed Volt meter doesn't begin to show any form of charging right after engine startup. It takes oh, maybe a few seconds for the meter's needle to move over from about 11-12 volts, to around 14+ volts. Thanks for that info. Good think you boys know about this stuff.
Scott
 
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