Author Topic: R1200GS Hex head O2 sensors fun  (Read 3440 times)

botus

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R1200GS Hex head O2 sensors fun
« on: July 12, 2023, 12:43:17 PM »
Any experts....   bikes on 37k and the CAT sensors have only done 15k active life (but been in there all along)

the bike has had 4 years of being strange....  often seems ambient temperature related - when above 24C and it loves life, below it has days of running like an utter dog....

it all went wrong after an i-level update where it got a new engine map in 2018 (that was made available, but never put on this bike, some 10 years prior) - from then on in it never ran as well as it did on the old map - and in cold conditions was massively over-fueling...

turns out when the map is that updated they should clear the adaptions and the bike needs its CAT sensors in and the vehicle std - so it can re adapt across all weathers, temps, altitudes etc. to the new world...  but coz I was running a PC3 that never happened...   

Anyway, eventually put it to stock wiped the adaptions and it would be OK for 250 miles then go mad over and over....

then last week the terrible over-fulling idle came with a vengeance and stayed...  Putting the GS911 on, the CAT sensors were operating but each doing quite different stuff and the short term adaptions were stuck on 15% too much on cyl 1 and stayed totally static

I knew the right pot has slight corrosion on two pins of the CAT sensor and remade those but the bike is still the same...
So I decided to try swapping the CAT sensors side to side - and the fault moves - so clearly one is not happy - but I can't work out which...

Got one replacement sensor so I could play quick - only two of the four pins get any continuity on all 3 sensors  - on 200 ohms I get 0.6 on one original and on the secondhand part I picked up - but as I wanted to play fast it was an old part I could get locally that day - and so I might have 2 dead and one OK, or even 3 in different states of dying...???

Fitted the newer bit in left pot, started the bike and almost straightaway the 15% (now on cyl 2 as I'd swapped sensors) starts climbing down and the 0.7% on the other cyl 1 climbed.  But then never stopped and it just reversed the fault (back to how it was the day before I stated to play musical chairs....)

that muddled my simple brain - as I'd suspected the right pot sensor died and I'd moved it to the left...   I then replaced the sensor on the left with a replacement and cyl 1 went normal but cyl 2 went mad...

then I realised I actually have no idea which is cyl 1 - I always assumed its the left pot (when sat on the bike) - I couldn't locate anything on the internet, and then I may have muddled my brain again - as I took out whats now on the right pot and was going to refit (what would have been) its original sensor - I'd wanted to check if the resistance on these wires and it was showing a difference between each sensor where one is obviously dead... and I forgot which I was putting back ...

but what caused me to get muddled - was of the three, one original had a different reading to the other two (but no idea which was correct) - then once hot all three were reading the same - then one wasn't as it cooled, then did, then didn't... the one I now think is the worst sensor gets 6.5 not 0.6 ohms on 200 setting...(and came off the left pot)

in the end, on the right pot I put back the what I believed was the original sensor  - but in reality put back the duff one I had just taken out...  Now with the original right sensor, the bike has started to behave on both pots and the O2 sensor voltages and the short term trims as seen on the GS911 looked normal -

So I guess it was the original left sensor that had been dead all along and I got muddled - But if that's true cyl 1 would have to be the right pot and or BMW deliberately mess up the fueling pushing 15% more on the opposite cyl to the one where the sensor fails just to make the bike run stupid and confuse people?

either way if you disconnect a sensor the fueling goes to much better than a lying / dead sensor


« Last Edit: July 12, 2023, 01:12:08 PM by botus »

Jughead

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Re: R1200GS Hex head O2 sensors fun
« Reply #1 on: July 12, 2023, 07:52:38 PM »
Firstly, an easy way to determine which cylinder is No:1.  Unplug the injector plug.  Start and run the engine for a few seconds. (Yes, it will misfire).

Now run an Autoscan and see which cylinder reflects the injector fault.

WRT the lambda sensors.  Measuring the resistance will not tell you anything beneficial.  To test them correctly,  remove them and connect a voltmeter to the black and grey wires.  Now heat the end of the sensor with a butane torch. (Don't be afraid to make them red hot)  While heating it the voltage should climb to around 800 - 900mV on a good sensor.
« Last Edit: July 13, 2023, 08:51:46 AM by Jughead »

botus

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Re: R1200GS Hex head O2 sensors fun
« Reply #2 on: July 13, 2023, 11:46:30 AM »
Firstly, an easy way to determine which cylinder is No:1.  Unplug the injector plug.  Start and run the engine for a few seconds. (Yes, it will misfire).

Now run an Autoscan and see which cylinder reflects the injector fault.

WRT the lambda sensors.  Measuring the resistance will not tell you anything beneficial.  To test them correctly,  remove them and connect a voltmeter to the black and grey wires.  Now heat the end of the sensor with a butane torch. (Don't be afraid to make them red hot)  While heating it the voltage should climb to around 800 - 900mV on a good sensor.


thanks nice info on testing....

apparently the right pot (as you sit on the bike) is cyl 1


botus

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Re: R1200GS Hex head O2 sensors fun
« Reply #3 on: August 15, 2023, 01:53:04 PM »
so one of the sensors had died, as I could get hold of a used one quick - I went that route

the bike idles better, and the adaptions have been wandering back to normal - rather a good trick that if BOTH the CAT sensors are disconnected the bike rides normal and stays normal - but if one is dead, it trashes the fuelling adaptions deliberately on the other pot

BM want £270 each - the same part on aliexpress is £25 delivered to your door faster....

« Last Edit: September 04, 2023, 11:20:02 AM by botus »