FJRiders.com

Posted: **Fri Sep 06, 2024 7:58 am**

I'm hot on the trail of resolving something and the fuel trim data that's added from the MAP and O2 sensor is basically full of data I need to purge out. I know it constantly updates that and over time it will resolve itself, but I'd like to be able to clear it out. I've heard disconnecting the battery for 30 minutes will do it but I've also been told that it will not, it has to be done via a diagnostic computer. I'm not sure which one of those is correct.

Is there a way on a Gen 3 to purge that short term fuel trim data?

Posted: **Fri Sep 06, 2024 9:43 am**

Festus wrote: ↑Fri Sep 06, 2024 7:58 am I'm hot on the trail of resolving something and the fuel trim data that's added from the MAP and O2 sensor is basically full of data I need to purge out. I know it constantly updates that and over time it will resolve itself, but I'd like to be able to clear it out. I've heard disconnecting the battery for 30 minutes will do it but I've also been told that it will not, it has to be done via a diagnostic computer. I'm not sure which one of those is correct.

Is there a way on a Gen 3 to purge that short term fuel trim data?

There is only person we know who might definitively answer that question.

Ivan.

dan

Posted: **Fri Sep 06, 2024 10:31 am**

Just to be clear, from my understanding, there is the base fuel map, and then there's the "trimmed" data that is applied constantly that refines the data to the conditions. It's my understanding that you can clear that "trimmed" data which reverts it back to the base fuel map and then it'll start building the file again with fresh data.

Over time, it will correct itself, but clearing it out would give instant feedback. I'm good either way, just was hoping there's a quick fix to delete the "trimmed' data.

Posted: **Fri Sep 06, 2024 12:28 pm**

Are you certain the 'Trimmed Data' as you call it is stored? And not just real-time adjustment?

Posted: **Fri Sep 06, 2024 12:30 pm**

SkooterG wrote: ↑Fri Sep 06, 2024 12:28 pm Are you certain the 'Trimmed Data' as you call it is stored? And not just real-time adjustment?

Reasonably sure. I believe it creates sort of a mini map of adjustments over time and the master fuel table is referenced when needed to prevent wide swings outside the normal. Could be wrong. Finding people that know specifically about the FJR is like finding a FRJ rider in their 20's.

Posted: **Fri Sep 06, 2024 3:18 pm**

I am sure you are correct about the trim data being learned. On the BMW GS's there is a tool called GS-911 that allows you to reset all the fuel trims, recalibrate the throttle grip, throttle valve, DTC, ESA, and transmission (quick shifter). I've never heard of a tool like that for FJR's. I am sure dealer software would do it, but wouldn't trust one of their lackies who hardly ever sees an FJR to do it. Probably brick it. Have you looked at Service Manual?

Posted: **Fri Sep 06, 2024 5:46 pm**

AFAIK, you cannot reset the ECU by unplugging it...... your questions should be directed to Ivan.
As for my non-expert opinion, I would think the data is not stored in EEPROM, so should erase when you shut the ignition off... or at least constantly overwritten when you ride.
There is only one thing you can reset in DiAG, that is the Idle Speed Control learning, but I'd think that only affects idle on the throttle by wire. If you like, reset it anyway whether it needs it or not.... in DiAG scroll to d:67....

Posted: **Fri Sep 06, 2024 6:17 pm**

It was my early understanding that it's written to RAM and will be erased if the battery was unplugged for 30 minutes but that info was contradicted by someone that knows a lot more than the people that said it did. His response was he was unaware of any brands that cleared like that.

No worries, I'll let it relearn itself. I would think it has to be holding onto data info for longer than real time, otherwise, if you lived and road above 6,000 ft, every time you started it, the bike would be running poorly until it got enough data to correct itself. However, once it learns the data, it uses it moving forward and then I'm sure it becomes a situation where it's dropping the old data off the back end and adding new data to the front end.

It's all good. I'm not going to bother Ivan when I know he's busy, he's not making a penny from taking a call, and it'll fix itself over time.

Posted: **Fri Sep 06, 2024 9:16 pm**

Festus wrote: ↑Fri Sep 06, 2024 6:17 pm otherwise, if you lived and road above 6,000 ft, every time you started it, the bike would be running poorly until it got enough data to correct itself.

My SWAG here but as soon as you turn on the ignition the MAP will tell the ECU all it needs to know about real-time temperature and elevation and immediately adjust accordingly.

Posted: **Fri Sep 06, 2024 9:42 pm**

SkooterG wrote: ↑Fri Sep 06, 2024 9:16 pm
Festus wrote: ↑Fri Sep 06, 2024 6:17 pm otherwise, if you lived and road above 6,000 ft, every time you started it, the bike would be running poorly until it got enough data to correct itself.
My SWAG here but as soon as you turn on the ignition the MAP will tell the ECU all it needs to know about real-time temperature and elevation and immediately adjust accordingly.

It doesn’t.

Best I can tell is it’s just going to take about an hour of riding with multiple starts, cold starts. It’ll fix itself.

Posted: **Sat Sep 07, 2024 9:03 am**

Festus wrote: ↑Fri Sep 06, 2024 7:58 am I'm hot on the trail of resolving something and the fuel trim data that's added from the MAP and O2 sensor is basically full of data I need to purge out. I know it constantly updates that and over time it will resolve itself, but I'd like to be able to clear it out. I've heard disconnecting the battery for 30 minutes will do it but I've also been told that it will not, it has to be done via a diagnostic computer. I'm not sure which one of those is correct.

Is there a way on a Gen 3 to purge that short term fuel trim data?

I'm trying to learn something. Why is the data you want to purge "undesireable"? Is this causing some ridability or other issues? How did you discover the "problem" - if it is a problem?

Posted: **Sat Sep 07, 2024 9:25 am**

The bike had an issue which caused the "temporary fuel map" to be built on bad data. Imagine an oxygen sensor going bad and getting the wrong reading. It's going to send that data to the ECU and the ECU is going to change the temporary map to add or subtract fuel to make the oxygen sensor number come out right. Therefore, the temporary map is correct for the bad O2 sensor but if you replace the O2 sensor, then the map sees the numbers from the new sensor and applies the fuel requirements from the old one, meaning it could be too much or too little fuel being supplied. You'd want to change the sensor and then clear the data, so the ECU will revert back to the factory fuel map and start building a new temporary fuel map based on the new sensor data.

Make sense?

As mentioned, it will self correct, but that takes time and miles, and some times it would be nice to clear the data and get instant correction.

Posted: **Sat Sep 07, 2024 1:01 pm**

Festus wrote: ↑Fri Sep 06, 2024 9:42 pm
SkooterG wrote: ↑Fri Sep 06, 2024 9:16 pm
Festus wrote: ↑Fri Sep 06, 2024 6:17 pm otherwise, if you lived and road above 6,000 ft, every time you started it, the bike would be running poorly until it got enough data to correct itself.
My SWAG here but as soon as you turn on the ignition the MAP will tell the ECU all it needs to know about real-time temperature and elevation and immediately adjust accordingly.
It doesn’t.

Best I can tell is it’s just going to take about an hour of riding with multiple starts, cold starts. It’ll fix itself.

Interesting. I am still having trouble wrapping my head around this. So, if you trailer an FJR from San Diego at sea level up to the Sierra Nevada mountains at 9,000' elevation it will run like crap initially? I just don't see that happening. The MAP and sensors will tell the ECU about current real-time temperature and air density and adjust the base map accordingly so it will start and run correctly.

Posted: **Sat Sep 07, 2024 1:26 pm**

Festus wrote: ↑Sat Sep 07, 2024 9:25 am The bike had an issue which caused the "temporary fuel map" to be built on bad data. Imagine an oxygen sensor going bad and getting the wrong reading. It's going to send that data to the ECU and the ECU is going to change the temporary map to add or subtract fuel to make the oxygen sensor number come out right. Therefore, the temporary map is correct for the bad O2 sensor but if you replace the O2 sensor, then the map sees the numbers from the new sensor and applies the fuel requirements from the old one, meaning it could be too much or too little fuel being supplied. You'd want to change the sensor and then clear the data, so the ECU will revert back to the factory fuel map and start building a new temporary fuel map based on the new sensor data.

Make sense?

As mentioned, it will self correct, but that takes time and miles, and some times it would be nice to clear the data and get instant correction.

I understand generally how the ECU and it's sensors work on our motorcycles (and all "vehicles" FTM). So... did your O2 sensor go bad and need replacement? At the risk of prying, that's really what I was asking.

Posted: **Sat Sep 07, 2024 1:32 pm**

I don't know that it'll run like crap but I believe if you were measuring the fuel/air mixture coming out of the exhaust, it would be vastly different on start up than it would after being there for several hours. I think you'd see 2 very different sets of numbers.

Take the reading at sea level, it's probably 16-17, trailer it to 9,000ft, start it and that measurement is probably 12-13, then run it for a few hours and let it adjust, and check it again and it's probably at 16-17. The bike is adjusting as it's being ridden. That's the beauty of fuel injection/sensors/ECU's.

Maybe the FJR isn't like that. I don't know, but from my understanding that's how they all work, and Toter has confirmed that's how the BMW works up above.

Posted: **Sat Sep 07, 2024 1:33 pm**

Hppants wrote: ↑Sat Sep 07, 2024 1:26 pm I understand generally how the ECU and it's sensors work on our motorcycles (and all "vehicles" FTM). So... did your O2 sensor go bad and need replacement? At the risk of prying, that's really what I was asking.

Nope, I was just using that as an example. Not my bike, just trying to help resolve an issue.

Posted: **Sat Sep 07, 2024 4:31 pm**

I'm with SkooterG.... MAP sensor data is instantaneous when you turn the ignition on, there's no "somewhere a few hours later". Coolant temp, ambient temp, etc. also. 02 instantly reports what it's seeing...... if it's RAM, RAM loses it's info the minute the power is shut off... i.e., ignition key.

Posted: **Sat Sep 07, 2024 6:23 pm**

I don't know the specifics of what's instant and what's not instant but I do know that there is an amended map that's used that's built on the fly that's stored and used over time. What data makes that map, I do not have the info to, but I suspect it's most all relative sensors and readings.

Posted: **Sun Sep 08, 2024 7:24 pm**

Seems to have reset itself throughout the day of riding.

Posted: **Mon Sep 09, 2024 1:31 am**

Festus wrote: ↑Sun Sep 08, 2024 7:24 pm Seems to have reset itself throughout the day of riding.

Ahhhhh...... the ol 'Stress less, Ride more'.

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