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Need Help Code intermittently comes up, something to do with o2 sensors.

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Kiwidude

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Perth, Western Australia
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2023 BMW R18 Classic
My R18 classic converted to a Rogue motorcyles bobber has recently had a custom full system exhaust put on. O2 sensors transferred over etc, servo's removed under bike and servo dummies put in, the servo's were removed and dummies put in a while back when it had the pro race slip ons on it.. Sounds awesome and runs sweet. Every 4 or 5 rides I go out on it the check engine light comes on, I put my Hex GS-911 on it and its a plausibility of the LSU, minimum error... have attached screenshot of it.. now that is something to do with the o2 sensors.. we checked them out to make sure they were tight and seated properly, all good...I can go for a long ride, over 100kms, no code, but it seems to pop up when warm after a number of rides.. I have noticed no consistency when this happens, its happened under acceleration hard, happened calmly going through the gears, so far when bike warmed up, otherwise runs great and the confusing part it only happens every now and then, thank god for the GS-911 so i can clear the code and get the check engine light to go off... any ideas from anyone or has anyone had something similar...bike8.webp
 

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Maybe just a faulty sensor or on edge of failing; perhaps, roll the sensors and see if the failure moves to the other exhaust side, following the suspect sensor?
 
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If it’s not the above I can only think all those mods have taken the engine emissions outside of its pre-determined limits, whatever they may be. The CanBus isn’t happy.🤷‍♂️
 
Kiwidude said:
My R18 classic converted to a Rogue motorcyles bobber has recently had a custom full system exhaust put on. O2 sensors transferred over etc, servo's removed under bike and servo dummies put in, the servo's were removed and dummies put in a while back when it had the pro race slip ons on it.. Sounds awesome and runs sweet. Every 4 or 5 rides I go out on it the check engine light comes on, I put my Hex GS-911 on it and its a plausibility of the LSU, minimum error... have attached screenshot of it.. now that is something to do with the o2 sensors.. we checked them out to make sure they were tight and seated properly, all good...I can go for a long ride, over 100kms, no code, but it seems to pop up when warm after a number of rides.. I have noticed no consistency when this happens, its happened under acceleration hard, happened calmly going through the gears, so far when bike warmed up, otherwise runs great and the confusing part it only happens every now and then, thank god for the GS-911 so i can clear the code and get the check engine light to go off... any ideas from anyone or has anyone had something similar...View attachment 15738
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Just checking in.. any luck with understanding the failure?
 
I would start with deleting all adaptions...... then.....

Check....
1. O2 Sensor... inc connector etc....
2. Air leak (ie vacumm side of things).... then exhaust.

Might as well swap the servo budies over and see if the fault moves....

I've not seen anything online about this..... most BMW engine code stuff online is auto based, and these codes don't seem to be mentioned in that world (I had a brief look).

Whilst this link isn't relevant specifically..... a read does show how weird things can get (buried in there is something about reseting adaptions) ... https://bimmerprofs.com/12c401-plausibility-signal-activity-low/
 
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Kiwidude said:
My R18 classic converted to a Rogue motorcyles bobber has recently had a custom full system exhaust put on. O2 sensors transferred over etc, servo's removed under bike and servo dummies put in, the servo's were removed and dummies put in a while back when it had the pro race slip ons on it.. Sounds awesome and runs sweet. Every 4 or 5 rides I go out on it the check engine light comes on, I put my Hex GS-911 on it and its a plausibility of the LSU, minimum error... have attached screenshot of it.. now that is something to do with the o2 sensors.. we checked them out to make sure they were tight and seated properly, all good...I can go for a long ride, over 100kms, no code, but it seems to pop up when warm after a number of rides.. I have noticed no consistency when this happens, its happened under acceleration hard, happened calmly going through the gears, so far when bike warmed up, otherwise runs great and the confusing part it only happens every now and then, thank god for the GS-911 so i can clear the code and get the check engine light to go off... any ideas from anyone or has anyone had something similar...View attachment 15738
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Did this ever get resolved..? If so, what was it?
 
TL;dr: Your free-flowing exhaust might be adversely impacting how your rear O2 sensors are reading Lambda under hard acceleration, as exhaust gasses aren't lingering around the sensor long enough.

After reviewing BMW auto forums that list a similar error, it strikes me that, also looking at your custom exhaust setup, that under hard acceleration, the exhaust gases rush past the O2 sensors too quickly for them to give an expected Lambda reading.

On the auto forums, these errors would point to unmetered air getting past the air intake sensor/MAF. Bottom line is that the O2 sensors are seeing extra oxygen, or could not be reacting fast enough to changes in Lambda (possible tired O2 sensor). The only true test would be to hook an oscilloscope to the O2 leads and log the response time of the sensor to Lambda changes.

I did a quick Google search on free flow exhausts and how they impact O2 sensors. The fancy Google AI came back with:

"A free-flow exhaust system can often lead to issues with oxygen sensors, primarily because the altered exhaust flow can disrupt the sensor's ability to accurately measure the air-fuel ratio, potentially causing the engine to run too lean or too rich, resulting in decreased fuel efficiency, rough idling, and check engine lights."

That said, here's my logic on your situation, and it assumes your rear O2 sensors are ~12" before the exhaust tip, and you have no vacuum leaks in the intake manifold:

You report that under normal operation, no Lambda errors are reported.
However, under hard acceleration, Lambda errors pop up.
Under normal operation, the O2 sensors must be receiving enough exhaust gas to provide a plausible Lambda reading.
However, under hard acceleration, the O2 sensors aren't able to accurately measure the exhaust gas, as it's literally, rushing too fast past the O2 sensors and not lingering long enough around the sensor.
Conclusion: Either the O2 sensors are placed too far back in the exhaust pipe, thus exhaust gasses can't dwell long enough for the sensor to react, or the O2 sensor is dirty/worn out.

Caveat: I can't zoom in on your photo, so I can't accurately determine how far your O2 sensors are up-pipe.

I do tend to overthink things, so obviously, check obvious trouble spots, like worn/chafed wiring, loose connectors, and dirty O2 sensors first ;).

Mike
 
Page 24 of Rider’s manual ( Aust. ) ; when ECM symbol lights up , possible cause is that ECM has diagnosed a fault that effects pollutant emissions . Due to CATS removed ?
 
no that is incorrect, i know of a few r18's with cat's removed, no fault.. more likely the positioning of the sensors in the aftermarket pipes taking into consideration length and diameter.
 
AngryBaldMan said:
You think there will be a better price in a few weeks?
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Yeah.... either 10 or 15% for black friday....

Their last year instagram post....


bt_moto_
47w
Our biggest sale of the year is LIVE! Get 15% off all BT Moto tuning and BT Moto branded parts. You can even save on 2025 BMW and Ducati flashing now!

This sale ends December 11
 
I am a bit surprised that the R18 community has not (yet) used the in the car tuning world ubiquitous spacer for the O2 sensor. Costs beer money and Bob´s your uncle.

As to tuning the R18, my base model is grunty enough really. I have the Sprint (dry) filter and side intake planned because I think the engine deserves to súck less. The flap servos I have deleted for just that bit more burble but am véry pleased it has not increased the exhaust note when riding.

Even with 15% the BT is still a lot of money to solve a problem I do not perceive.
 
interesting thread here, but for those of us who still have stock headers and pipes (not including upgraded cans), how is the decat procedure done? Do I open the pipe from below and extract them on each side or is there a bypass available that plugs in or is welded into place? Thanks. BTW, I am happy with the increased exhaust note and burbbles on with my Vance & Hines cans.
 
david.finkelstein said:
interesting thread here, but for those of us who still have stock headers and pipes (not including upgraded cans), how is the decat procedure done? Do I open the pipe from below and extract them on each side or is there a bypass available that plugs in or is welded into place? Thanks. BTW, I am happy with the increased exhaust note and burbbles on with my Vance & Hines cans.
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