CEL(check engine light) came on for 2 seconds-why?

[user_deleted]

have 2007 Uly with 4000 miles on it. flawless condition, all stock, breather reroute and iridium tipped NGK plugs. never any issues with it, runs and starts flawlessly and i ride it gently. yesterday i'm cruising behind a slow car in 5th gear at about 2000rpm, got tired of following this cage so rolled throttle wide open and zipped around him. moments after passing i rolled out of throtle and CEL came on. at about 65mph i momentarily turned off kill switch and a second later turned it back on and CEL went off, never came on again, bike runs perfectly. anyone ever have this happen and if so, what might it have been? thanks for any insight.

 

[uly luigi]

May have had a misfire from the lugging, I have an '08 uly, and it does not like running that low in the revs, these engines are not real efficient below about 2500 rpm, I think the ecm may have leaned it out a little bit, then when you rolled on the throttle, it started to add some fuel, just as it got back to stoich, you shut it back down/got around the vehicle, so it was a little rich then, and the swings in the o2 sensor may have confused the ecm for a second or 2 and tripped the light, I wouldn't worry about it unless it starts to do it on a regular basis

 

[user_deleted]

thanks very much luigi for the info and what you described is exactly what happened and what i did. i should have dropped a gear and made the pass but these motors have so much torque i didn't feel the need to do so. nice thing is light went out and never came back on. think you nailed it. thanks again my friend for the advice.

 

[uly luigi]

No problem dude, that's why we are here

 

[djohnk]

I have another possible scenario: my CEL sometimes comes on when my exhaust valve sticks a little. I think it's stock programmed to open at a high RPM, it could have been that since it sounds like you were close to redline ... it could of tried to open, couldn't, then the CEL light went on. When you backed off the RPM since the valve was in the right position (closed), and you toggled the engine cut-off, the light went off (it probably would have turned of in a little bit on it's own).

I changed the programming on my ECM so the exhaust valve is closed up to 800rpm (for starting) open 800rpm to 3500rpm and closed above 3500rpm for quiet highway cruising. Since mine is opening and closing so much I get that momentary CEL every so often when it sticks a little, no worries.

 

[user_deleted]

djohnk: thanks for the response and i failed to mention i have hawkins muffler with power valve rendered inoperative. by that i mean the valve actuator on airbox still plugged in and functioning and cable hooked to muffler valve but no valve plate inside muffler. i think luigi nailed it precisely. the O2 sensor sensed rich condition when i rolled off throttle abruptly and just kicked on light. and i think you're correct in that the light would have eventually went out on its own. i would love to add a bit of fuel to the fuel curve map on the stock ECM but don't trust myself to do it. thanks again.