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.

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

I dont think they have ever been changed. Thanks for the help.

Right. So replace them.

Fix the P0147 heater code first.......bad sensors, fuse or wiring problem.

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?

or bad o2 sensor.


when the heater circuit IN the sensor opens up, the DME sees that and turns it off.

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

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?

@ 150,000 miles it's time to replace the o2 sensors. As Ard said, buy Bosch replacements. I did all of mine @ 118,000 miles after having intermittent o2 heater errors, and a lean code every now and then. Since replacing all 4 o2 sensors... no more codes. I think mine were around $350 for all 4 of them.

It may not solve all of your codes, and you may still need a MAF. But o2 sensors are a maintenance item and it's time yours were done.