Code 31

Some friends and I departed on Sat., May 31st on a four day trip from the Toronto area through New York, Vermont, New Hampshire, Maine and back. From the moment we left until we made our first (breakfast) stop, 164 kilometers (102 miles) later, the rain poured down on us pretty hard. About fifteen minutes before making our first stop I noticed the engine light had come on, but was not blinking. After breakfast, when I turned the key in the ignition I noticed error code 31 was displayed on the dash. I refueled and about 20 minutes down the road the engine light went off. The light has not come back on since (we covered an additional ~2,000 kilometers [1,243 miles] on that trip and I have done some other shorter rides since).

Any feedback would be appreciated.

Aside from the error code the trip was excellent! Kancamagus, #17, the Atlantic ocean, etc, etc, etc.

Error Codes 24, 31, 32: O2 sensor (inactive), (compensation stuck to upper limit), (compensation stuck to lower limit)

The FSM says that code 31 for your Gen I is:

The amount of air-fuel ratio feedback

compensation is maintained

continuously in the vicinity of the

upper limit (lean air-fuel ratio).

This is something that the ECU determines by reading various sensors. The item most likely to have caused your problem is a wet O2 sensor. Either water got into the wiring or the rain kept the sensor from getting hot enough to return a valid reading.

Most of the other things that would cause a code 31 are 'hard' problems like a defective harness or a blown ECU that won't self heal. The O2 is a 'soft' problem that can self heal when it dries out.

Keep an eye on it but don't worry.

Lot better than you'd get from your local service Dept I bet!

This is the only reference made to code 31 that I have been able to find on the internet: Link

Thanks for the help everyone...

DailyCommuter - you've got that right. After my local service depot writes up the work order it will take them three days before they can get to it - only to charge me $90 / hour. And each day they roll it out and rool it back in they bang my bike off the others around it.

I forgot to add that the yellow check engine light with any one of the codes that Iggy mentioned was not uncommon for many '03s and some '04s. The yellow check engine light often came on right after washing the motorcycle or during a rain ride. If the light only comes on under specific wet conditions there is no worry. If the light comes on for no apparent reason and stays on or comes back on right after being reset you may want to have someone look at the problem.

If your CE lights does come on fitting the pattern for an actual failure I'd be willing to bet that 99.9% of the time the problem will be related to the O2 sensor unless you have had the ECU connector off for some reason, like while doing a Barbarian jumper mod.