Intermittent check engine light

[Mike_D]

I'm running a 2008 S2R1K with full arrow exhaust and the Fat Duc 02 modulator.  Three or four times today, the check engine light would come on for about 2 minutes, then go out.  It always occurred a couple minutes after a short break when the bike was shut off.  The bike seemed to run fine--no sputtering, surging, or loss of power.  I'm wondering if it's the ECU trying to adjust to the Fat Duc which is set just on the rich side of halfway.  Any ideas what could be causing this?  Thanx.

[SubyBoyRS]

I've had this happen once to me.  I have a 2007 S2R1000, it only happened once.  I didn't notice anything different about how the bike ran, the light was only on for a few minutes like yours.  I do recall a thread fatduc himself posted about how he has experienced the same thing.  Not sure there is a reason or solution yet.

[Mike_D]

I e-mailed Jason at Fat Duc and here is his reply for any of you who are running the modulator.  Thanks Jason--you rawk! 

"Yes, we have experienced this during product development and in normal use.  The occasional check engine light is most likely due to excess carbon build up on the O2 Sensor.  Only a very small percentage of bikes (including mine) have exhibited this side effect when the variable trimmer is set towards the richer side.  Each individual bike is somewhat different due to normal manufacture's and part suppliers tolerances.  The carbon build happens after extended periods of idling or after extended periods of cruising.  It should go away after revving the motor and clearing of the sensor off with the hot exhaust gases.  One thing we learned when my Ducati tech was dynoing/testing the product is it does run a bit richer at idle than it does during normal operation.  He wasn't concerned about it, but you wouldn't want to let your bike sit and idle for long, long periods at a time (30 - 40+ minutes).  You could try to set the variable trimmer slightly leaner to see if the CEL comes on less frequently, but you want to make very small adjustments on the trimmer and ride for a couple of days.  You'll want to find the leanest setting on the
O2 Manipulator that still eliminates the surging and other lean fueling problems."

[jstanton]

I just put in a new battery.  It's a Shorai lithium ion.  Anyway, I'm pretty careful and took my time and did everything right, as far as I could tell.  The bike starts right up and runs fine, so I am assuming all is as it should be.. But I took her out for about a 30 mile round trip into town and started getting these check engine light episodes.  The first one scared me enough that I pulled off the road and shut down.  I checked the sight glass and the oil is fine.  I walked around the bike and couldn't find anything out of order.  So I restarted and after a minute the light came back on.  I tried shutting down at a light and that seemed to fix it.  But it kept popping back on again sort of randomly, then going back off just as randomly.  It finally went off for the last time after I took a long leaning left, so now I'm wondering if there's something about that.  I have rechecked all the connections and everything looks just fine.  Anyone have a similar experience?