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Discussion Starter · #1 ·
Hey guys, could really use a bump on this thread. Ive got 4 o2 sensor codes showing lean upstream and downstream as well as a code for connection to pcm. Car has been stumbling at times for months before the codes showed up. Also, having intermittent random misfire codes. Could use some advice....is this a bad o2 sensor leaning out banks1 & 2, not communicating with the computer, or good sensors indicating vacuum leak or perhaps poor fuel delivery. Which of the two scenarios is more likely to accompany random misfire? Thanks in advance.

Codes are
P 0300
P 0147
P0149
P114D
P2195
P2197
 

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Need more info. Model, mileage, recent work, etc. Are you using a generic scanner or a BMW specific scanner?
 

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Discussion Starter · #3 ·
Its a BMW X5 E70 3.0L inline six, n52b30 with 150k on it. 1 year ago I replaced the plugs and air filter oil change with filter. Two weeks ago I had to replace the fuel pump...now this. Tomorrow I can check the fuel pressure at the rail.
 

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from xoutpost:

when did you last replace the O2 sensors? They are maintenance items. miles not 'days or years ago'
 

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Discussion Starter · #7 ·
Okay...this morning I tried to start the engine, stumbled poorly then died...no start. Scratched my head...then pulled the MAF sensor plug from the air box, tried again and it cranked smoothly and idled like normal, very well. Now, running without the MAF plugged in, im showing code P114D lean after CAT, and P2195 and P2197. Have I isolated the problem to the MAF sensor? I ordered a BMW specific reader with access to live stream data, will arrive Sunday. I cant afford to swing and miss at hundreds of dollars per sensor. Thank you guys so much, my wife and I NEED this car desperately.
 

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To the best of my knowledge they have never beem changed.
I don't understand this.. O2 sensors should be replaced at 100k. Or sooner. They are a KNOWN. DOCUMENTED consumable maintenance item.

Yet you are chasing issues, ordering parts, FEARFUL of costs- and blithely dirving a car you cannot afford to maintain.

This is a CLASSIC case of 2/3/4 owner....people ignore maintenance...then when issues come up, there is a TON of deferred maintenance that confuse the ability to properly diagnoses. You are stuck FIRST addressing everything that should have been done...and only then can you determine what (if anything) has actually failed.

THis idea of 'just tell me the ONE think that I need to buy, I'll continue to avoid fixing or maintaining anything they ISNT causing my CEL today.

Good luck...
 

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Discussion Starter · #9 ·
I'm the 2nd owner, only had it for 12 months and these are my first issues. Sorry I havnt replaced every sensor filter and hose yet, but really, thanks for your time. Anyone else know if a failed MAF can cause o2 sensors to read lean?
 

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Discussion Starter · #10 ·
Also, previous owner had dealership scheduled maintenance every 2 years since 2008, but I can only assume the dealer would have replaced consumables.
 

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Also, previous owner had dealership scheduled maintenance every 2 years since 2008, but I can only assume the dealer would have replaced consumables.
so you have at least one confirmed, bad O2 sensor... and you are gonna assume they have been replaced...you will ignore advice...and convince yourself its a MAF? Because something changes for the good when you disconnect it?

I am FAR from a 'replace everything' kind of guy. But when the codes tell you there is a bad O2, or wire to it, only an [redacted to avoid BF violations] looks elsewhere.

Go for it buddy, buy a new MAF... Cheap is expensive.
 

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Discussion Starter · #12 ·
Hmm...and your advice was "CEL showing lean on banks 1 and 2 upstream and down so replace all 4 O2 sensors". Correct? If the MAF was good the car wouldnt refuse to start and idle with it connected and run fine without it. Diagnosing the proper sensor with live stream data scanner, like I said I would, is the more efficient way to go about this job. Proper diagnostics before purchasing parrs is what separtes backyard from proper mechanic. I guess uf ur a rich So-Cal yuppy you can just throw money at everything and rule it all out lol either way nail in the coffin on the MAF unless you have any contradictory/useful information. You have too many assumptions about my approach that incorrect to be helpful.
 

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Discussion Starter · #13 ·
Low battery voltage could cause com connection error unless correct, may be worth checking the battery if all o2 read in spec
 

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maybe 02 sensors are maintenance items in the bmw world. I know bmw has lists a 100 000k life but for every other manufacturer...they are only replaced when they fail.

maybe the 02 r reading lean due to low fuel pressure. check the fuel trim at idle and under load at 2500 rpm. If its lean at idle but ok at 2500 the fuel pressure is good...its a vacuum leak. If its lean only under load I'd check the fuel pressure.

check the freeze frame data...what rpm was the engine at when the lean 02 dtc set.
 

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Discussion Starter · #15 ·
Sounds like a plan, ive got a proper scanner with freeze live stream etc for BMW coming along with MAF Sunday...need both no matter what. Thanks for the fuel pointers, if need be ill make a smoke tester and follow up next week. If nothing else I hope someone will find all this dialogue useful one day. Stick it to the stealership when u can and dont waste part$!
 

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Why not clean your MAF with MAF cleaner and see if that helps. Watch live data on fuel trims as suggested and see if you really need to at least replace that one o2 sensor or it’s another issue. I’m guilty of being on my original 4 o2 sensors at 163,000 miles. I’ll replace them sometime soon as I bet they are not as effective as they once were. On my Lexus, each time I had a fault code for the o2 sensor it was indeed the o2 sensor that failed. I drove that to 172,000 miles from new.


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Also. I doubt the o2 sensors were ever replaced in your case. If they were you could get the record of it. When I read over my factory maintenance schedule I don’t even see them as an inspection point. It’s probably about $600 to replace all 4 o2 sensors.


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maybe 02 sensors are maintenance items in the bmw world. I know bmw has lists a 100 000k life but for every other manufacturer...they are only replaced when they fail.
he has failed o2 sensor codes. (when the internal o2 heater opens up you get that code)

So what do YOU think would be a reason to replace an O2 sensor. In other words how do you determine one has failed?????

Oh, you just need to replace the upstream O2. THAT is the one that is used to drive AFR.
 

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Hmm...and your advice was "CEL showing lean on banks 1 and 2 upstream and down so replace all 4 O2 sensors". Correct? If the MAF was good the car wouldnt refuse to start and idle with it connected and run fine without it. Diagnosing the proper sensor with live stream data scanner, like I said I would, is the more efficient way to go about this job. Proper diagnostics before purchasing parrs is what separtes backyard from proper mechanic. I guess uf ur a rich So-Cal yuppy you can just throw money at everything and rule it all out lol either way nail in the coffin on the MAF unless you have any contradictory/useful information. You have too many assumptions about my approach that incorrect to be helpful.
You disconnect the maf on a lean motor and it runs right so you ordered a MAF?! And are claiming you are some genius avoiding needlessly throwing parts at a car?

Ive seen nothing out of you that qualifes as a 'proper diagnostic'. What are you pre-cat o2s doing? Have you logged each of these to see how they are transitioning?
 

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Also, previous owner had dealership scheduled maintenance every 2 years since 2008, but I can only assume the dealer would have replaced consumables.
Call the Service Manager of that dealership if you already don't have all the service records and do your due diligence. Start there. It takes time to get to "know" your new vehicle. I'm going through that right now. Yea you can get online with some VIN decoder but the internet doesn't let you ask questions [or build a relationship] Just my $2...

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