ECU / Choke Problem?

Whenever I go on a trip into the mountains, it seems that my '04 coughs and sputters going through the warm up process. the "Check Engine" light comes on until the bike is completely warmed up and then the light goes out and the bike runs normally.

This problem first occurred in a X-country trip from Oregon to the Black Hills. Then again on another X-country to West Virginia the next year. Most recently I was in Idaho at maybe 1200 feet elevation or so and the problem surfaced again.

What is common is (1) It always happens on very long trips and (2) always in some kind of altitude. I live at around 300 feet above sea level, and I never have this problem at home.

Any ideas as to what's going on? I'm thinking ECU. But what do I know? I just ride the damn thing.

The good news? At 40,000 miles, no tick!

The 2007 bikes essentially all had this problem. Whenever the bike got up to about 4,000 feet the bike would surge, stall, etc. According to Yamaha if it is a faulty ECU if when you have the problem, turn the motor off and restart the bike. Doing that is suppose to reset the ECU for your current altitude and presumably temporarily solve the problem unless you go higher in altitude. I just had Yamaha replace the ECU, which was done for free since it was under warranty. My understanding is that a ECU cost about $650. Try the experiment.

Good luck. Brain Surgeon

Do this search

Altitude sickness site:fjrforum.com. On google

You guys noticed he had an 04, right?

odot said:

You guys noticed he had an 04, right?

Click to expand...

The Eskimo Texan is correct-E-mundo!

A 2004 FJR will have nothing to do with the Altitude/ECU issues experienced on 06/07 FJRs as the system is totally different.

Flylooper - something is obviously amiss, however I am not sure where to start looking.

There are no error codes you are receiving? Generally, there should be some error code associated with the yellow 'check engine' light.

I would go into diagnostic mode and check various sensors. I would start with the atmospheric and intake pressure sensors.

I am assuming you don't have a PCIII?

Damn I didn't notice that.

My '04 has had altitude sickness twice. The first time I had to cut short a ride with HerFJR and ZOOOMM because of it. In my cases the sickness hit when my bike was hot and had been shut off for ~1/2 hr. I discovered that when the sickness hit shutting it off and then restarting it again caused the problem to reset.

Low on the list of things to check is your gas tank venting. Checked my bike by opening the tank with a spare key while the engine was running – which quickly put that possibility to bed.

I agree with Skoot, when you are in an area where you have a problem, use the diAG to check the two pressure sensors. While troubleshooting after my second incident I swapped the two sensors to see if it made a difference. I haven't swapped them back, no need, they are identical. I also haven't had another altitude attack. The sensor under the tank, left end of the FI rail is easy to get to. The one under the seat cross bar, just behind the tool tray was challenging. Yamaha seems to find ways to make screw heads inaccessible. These sensors are delicate, resist the urge to stick something in the little air hole and never shoot air into the passage.

What are your choke & idle speeds? Does it smell like it is rich? Have you done a BJ? Do you have a PCIII? Does it do it independent of gas volume in your tank? Altitude creates a rich condition that the ECU has to compensate for, so a BJ adjustment and/or a PCIII will exacerbate the condition.

Good luck!

If it were me, I would check for corrosion in the engine wiring harness first, per this link..

https://www.fjrforum.com/forum//index.php?showtopic=22699

Easy enough to check, cheap to fix, and one less element in the chain of possibilities. Then I would get the TPS replaced under recall if not yet done so.

My two cents... I hope this helps!!