PLEASE HELP! P0171 ERROR

[Juggernaunt911]

Hey Everyone, just wanted to start off by saying that I love the site and found it very helpfull and full of very informative info.

I was driving along on the highway and suddenly the "service engine soon" warning lamp came up. Shortly after I had the diagnostic check done and the following error code came up "P0171 System to Lean Bank 1 (Left) " I did notice a little hesitation in power towards the hight RPM range as well.

It was pretty late in the day, so I thought to just fill up and try some fuel injectior/fuel line cleaner (not sure if that will help or not)

I am basically looking for suggestions (trying to avoid Dealer headache), I did some looking around through some related threads and they indicated that it can be possible vacume leaks,02 sensor and or MAF.

I am not too mechanically inclined but would like to take a stab at fixing this myself. Is there anyway I can clean the MAF or test this? To be honest I dont even know where it is located..lol

All suggestions and tip would help greatly!

Thanks for your help,
Tim

01 X5 4.4

[Weasel]

Likely not MAF or O2 sensor, but more likely a vacuum leak as a lean mixture indicates unmetered air getting into the manifold. I would check the crankcase vent hoses at the rear of the intake manifold as they are a common failpoint on the V8's at higher mileage.

With the plastic cover removed look at the rear of the intake manifold for these hoses... #'s 4 and 5. If they feel like modeling clay, that's likely the problem...

[Juggernaunt911]

Thanks Weasel56!

I will check it out today and let you know what I find. I appreciate your help on this!

[Juggernaunt911]

Well, the battle continues...... I checked out all the crankcase intake hoses for cracks and leaks, as well they did not appear to be moist or anything like that. All surrounding hoses appeared to be ok aswell as far as I can tell there are no apparent issues.

I guess the next think to go after would be the MAF sensor. I did snoop around and noticed that a couple of people mentioned that the aftermarket K@N filter are not so friendly for the MAF. I do have one installed in the vehicle, but did not suspect if this could be a problem.

I am pretty sure I located the MAF sensor (Right along the side hose from the air filter) but not too sure how to clean it. As well it seem that it is bolted down with non standard bolts...

Can someone help me out with this? is there a read up somewhere on how to Replace/Clean this sensor???


Thanks!

[Weasel]

None of the bolts on the X are going to be standard... they're all metric

There is commercially available mass air flow sensor cleaner available at any auto parts store (auto zone, etc.) Just remove the sensor and spray it down with the cleaner to remove the thin film of oil that can be deposited by the oiled K&N filter over time, but that usually would cause rich mixture faults... The lean faults are usually caused by vacuum leaks.

Where did you have the faults read, do you have a code reader or did you use a shop? With most vehicles, if you have a vacuum leak you just spray a flamable cleaner (brake parts cleaner, carb cleaner etc.) over the suspected areas/gaskets and listen for the idle to change speed or smooth out when you hit the leak and it sucks up the cleaner. But with the BMW's the engine computer compensates for it so fast you can't catch it like that, you have to watch the O2 sensor voltages in the diagnostic tester and when they peg and stick at the higher voltage (0.8 volts) thats when you hit the leak.

[Juggernaunt911]

I had the readings taken in a shop, unfortunatley I dont have a reading tester. I guess I will start off with the easy way first and try cleaning the MAF to see if that will cure the problem. If not I will keep hunting down the vaccume leak, using the method you mentioned above.

If by chance the cleaning of the MAF does fix the problem, will the fault/warning light go away on its own? Or is there a way I can reset it or do I have to take it to the shop and have them clear it?


Thanks

[Juggernaunt911]

Just another quick question non related to the Vaccume leak issue. A couple of weeks ago my "check brake linings" warning came on. I checked the pad wear and sure enough the front pads are low and need to be changed.

My question is do I need to replace the sensors along with the PADs? Or because my pads do need to be replaced, replacing them should be good enough?

Thanks

[flyingmachine]

Originally Posted by Juggernaunt911

Just another quick question non related to the Vaccume leak issue. A couple of weeks ago my "check brake linings" warning came on. I checked the pad wear and sure enough the front pads are low and need to be changed.

My question is do I need to replace the sensors along with the PADs? Or because my pads do need to be replaced, replacing them should be good enough?

Thanks

if you already have the warning, you will have to replace the sensor too.

[Juggernaunt911]

Is it just the one sensor on the front drivers side? is it just known as a "brake pad sensor" ?

[Weasel]

Yep. and to reset the light after replaced just turn the key on for 1 minute with the engine off.