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#1
09-13-2019, 12:19 AM
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Upstream/downstream lean on all O2 sensors with random misfire
Codes are
P 0300 P 0147 P0149 P114D P2195 P2197 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.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. 
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#6
09-13-2019, 06:28 PM
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Quote:
or bad o2 sensor. when the heater circuit IN the sensor opens up, the DME sees that and turns it off.
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#7
09-13-2019, 03:57 PM
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about 5 hours ago · #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?
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#8
09-13-2019, 06:35 PM
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Quote:
No, you have not. You are just taking stabs in the darkness due to your fear of spending money. When you disconnect the MAF, the engine sees this and defualts to a super rick map (to protect the motor). Since you car is running lean (due to who knows what, mayb 150,000 mile o2 sensors....?) when you unplug the maf, it restores the AFR. But sure, go ahead and replace the MAF...come back in a week with more head scratching. (You may think Im just being a dick, but trying o get your attention....) I do .ot nknow if it is your O2s, but the heater circut error tells me there is something up with the O2s. That is why my first question was when changed. When you came back with 'original 150k', its a no brainer to replace. (As pshovest suggests....replaicng the Os will also likely find any wiring issues.....oh, has anyone screwed with the O2 wiring? Hit anything?) anyway.... buy bosch OEM sensors- not BMW...Bosch with the proper connectors. Cheap. Maintenance items
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#9
09-14-2019, 09:24 AM
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O2 sensors usually don't fail in pairs, so I'd leave them alone. It may be your MAF, but a large vacuum leak will create lean conditions and driveability issues that will improve greatly when MAF is disconnected. There is a ~5/8" dia hose at rear of valve cover near firewall that is easy to damage during valve cover gasket replacement. Any work been done recently?
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#10
09-14-2019, 08:43 PM
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Quote:
Agree, for sure. When you see mutiple codes pop up in a single moment, that can be a clue as to what causes that unique pattern.... Unless one failed at 100k, one at 120k and one at 150k. for example. For all we know the CEL has been on for years, only once it starts driving like crap does this become urgent. Hypothetical of course, not speaking to OPs facts The heater circuit error cannot be explained by injectors...maf...fuel...pressure sensors..blah blah blah. Only one thing causes that code: an open circuit (ie no current) in the circuit that connects to the O2 sensor preheater. The list is short: O2 sensor, wire(s), connector, fuse. (Or...the DME is faulty, just to be accurate.) You ask 'any work done?'... indeed, someone messing with cats and O2s, might do that. Has anyone asked: "How long has the CEL been on?" "Did ALL these codes appear at the same time, just all at once and recently? "If not, how did these CELs evolve over time?
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