I think I'm having an ECU problem....bike is a 2007...Went riding yesterday and the temp here has been a nice 70 degrees during the day. Was riding at about 50-55mph for a 5 mile stretch of twistiesand came to a stoplight and once stopped I heard the fan running. Looked down and sure enough it was on. Looked at the temp gauge and it was only 180-185. Then it shut off while I was sitting there. Once home I was in the driveway about to pull in the garage and it came on again. Pulled it in, shut her off, then out of curiosity I hit the key again (not to start, only to see if the fan would come on) and the fan didn't come on. If the water temp is high enough, like 220, the fan should come on just by turning the key to the "on" position.
I'm not concerned with the fan coming on, but more concerned if my ECU is about to cause other problems. Any ideas on what may cause this?

 

Maybe you've got a nicked power wire that giving power to the fan control relay when its not supposed to?Fan relay has constant power coming from the fuse via the blue wire with orange tracer. It's only supposed to make connection to the black wire with orange tracer (theone that feeds power to the fan motor itself) when the signal from the ECM via the green wire with blue tracer. It could be possible that somehowpower is bypassing the relay from the blue/orange wire straight to the black/orange wire? Or maybe its just a faulty relay. Iwouldn't assume the worst right out of the gate. Does it still come on when it's supposed to (when temp reaches 220 I believe)?

 

Thanks for the reply ^. The fan still comes on at approx 220, as it should. I went riding today, the same as the other day when I first noticed it coming on, and the ambient temp was about the same. The fan never came on this time like it did the other day.
I was thinking the same thing with the relay, or the ECM. If it does it again, I'll start pulling the fairings and see if I can find a cause and bust out the meter.
I don't have the 06-07 shop manual, but I do have an 04-05 manual in pdf format...do you know if the wiring is the same between the 04-05 and 06-07?

 

I'm not sure if all the wiring is the same, but in the manual that I have it does differentiate between '04-'05 and after '05. However, the wires going to the fan relay are the same colors.

 

I've noticed the fan on my '07 doesn't seem to run strictly based on the displayed engine temp. While running some tests in my garageI noticed that anytime I held the RPM at a high idle (maybe 2500 RPM or so) for a few seconds the fan would come on. As soon as I let the RPM drop down tonormal idle,it would shut off. Maybe Honda has some programming in the ECU to predict an overheating event and nip it in the bud. Or maybe they're using the radiator fan underspecial conditions to circulate air around the headers to prevent heat buildup that coulddamage bodywork or electrical components. Special conditions might include high RPM orhigh intake air temp when the bike isnot moving or thetransmission isin neutral.