82 XJ750RJ Warning system acting up

So I'm 5 minutes into a 25-30 mph ride through the neighborhood and the Warning light comes on and all the LCDs are on. Neither the Check or Reset buttons do anything. Bike keeps on running just fine. Turn around and go back to the house. Turn the ignition off, restart and the Warning Light and LCDs come on and don't go through the normal system scan.

That's the second time this has happened. The first time was yesterday about 15 minutes into a ride. This time I was on the highway doing 50-60 mph about 4 miles from the house. It ran fine all the way back, but the Warning system went back to normal before I got back to the house.

Any advice would be greatly appreciated.

 

I have had similar things happen on my XJ11 and Venture. The fix was to take the LCD warning panel apart and re-solder all the connections on the circuit board. The vibrations over time weaken the solder joints and they fail.
A good thing to do first would be to check that the main plug on the panel is clean and in tight.

 

This is an indication that the CMS (Computer Monitoring System) has switched from an active state to a standby state. The CMS becomes active when the bike is started and one leg of the AC Generator that is routed to the CMS (white wire) provides the voltage to the CMS to activate it. This same leg of the AC Generator is also used to activate the latching headlight relay and therefore can aid in troubleshooting if the CMS does not go active when the bike is started.

This is a good suggestion, but I would also suggest checking the 3 pin connection for the stator to main harness that is located under the seat between the tank and fuse box. This connection is known to corrode and overheat.

You can also activate the CMS at the main harness stator mating connector with a jumper wire from the battery positive to one of the three pins. I am not sure if Yamaha was consistent on which pin, but with the key set to run and the connector disconnected then applying 12V from the battery one of the three should activate the CMS and the headlight relay.

 

Thank for the suggestions. I forgot to mention that the fuel gauge seemed to be working through all this. Does that changed any of the possible diagnoses? I'll start checking wires and connections as soon as I can get to it.

 

The fuel gauge is active without the bike running and is not affected by standby / active state - so I would say no it does not change the diagnoses.

 

Ok, thanks. I'll let all y'all know when I get it figured out. I sure hope I don't have to go in and resolder the board.⚡

 

+1

 

Thanks again for all the diagnostic suggestions. I finally got back to it. I started with Rooster53's suggestion since it was the easiest. The stator to main harness connector was melted and fused together. I had to Dremel the melted parts of the connector to get it apart. It was really ugly inside. Can't continue the troubleshootiing until I get a replacement. Hopefully all I need is the new connector.