M271 Check Engine Light P0171 possible fix...
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Joined: Feb 2006
Posts: 115
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From: Lakeland, FL
05 C230 Sport Sedan & 02 ML500
M271 Check Engine Light P0171 possible fix...
I know it been on here before but here's some more info on it. I checked that damn hose thats been said to sometimes cause that CEL error and sure enough mine was cracked. The part number of the hose that was on there is A271 018 04 82. The new hose I got from the dealer today ($12) is A217 018 12 82. The tech told me that the new part number means it should be improved. He also said that they have been replacing alot of those lately. For those that aren't sure where this hose is, its under the airbox and is probably the hardest thing to remove EVER ! (the airbox that is) Seriously, WTF you have to disconect like 6 things and then unscrew the MAF from the back of the airbox. Good Luck to anyone that tries this. IF you make it far enough to get the airbox off the hose connects at the top rear of the throttle boby and goes over to your left by the block. I'll take some pics and post them shortly. Its pretty simple to replace the hose. So if you're getting a P0171 error check that hose. Good Luck ...
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From: Charlotte, NC
2013 S550, CLS500, ‘03 SL500, “92 190E Sportline
I posted pics in my thread here: Pictures of hose Location
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Joined: Feb 2006
Posts: 115
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From: Lakeland, FL
05 C230 Sport Sedan & 02 ML500
Yeah, you can reach it without taking much off. Just remove the front intake part of the airbox with the hose and you should be able to pich it from there.
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From: Charlotte, NC
2013 S550, CLS500, ‘03 SL500, “92 190E Sportline
It sure was! If it's someone's first time doing this, it's a heck of a challenge. You have to find the screws, then you have to move the airbox in a certain manner to get it out, you have to disconnect the MAF, which involves getting to one screw which seems IMPOSSIBLE to reach. You need tools that are like 1/3 the size of their normal sizes lol...
We used a fuel line hose to fix mine. The rough idling and gas guzzling stopped, but I've been noticing lately that when I let off my gas pedal, the car seems to slow down roughly, it's not smooth... Perhaps the hose is kinked. I'll probably order the original hose from Mercedes and take a day to put it in. Better if I use my own clamp though, it seems like the hose from MB was made to chew through the hose.
By the way, the MAF sensor from MB is about $440. I may change mine, or just clean it soon, but I'll definetely buy it online and not from MB. Maybe its my MAF thats making my car slightly run rough when I let off the gas.
We used a fuel line hose to fix mine. The rough idling and gas guzzling stopped, but I've been noticing lately that when I let off my gas pedal, the car seems to slow down roughly, it's not smooth... Perhaps the hose is kinked. I'll probably order the original hose from Mercedes and take a day to put it in. Better if I use my own clamp though, it seems like the hose from MB was made to chew through the hose.
By the way, the MAF sensor from MB is about $440. I may change mine, or just clean it soon, but I'll definetely buy it online and not from MB. Maybe its my MAF thats making my car slightly run rough when I let off the gas.
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What I do the check that hose without all that hassle is run the engine, remove the intake tube. Spray carburetor cleaner all along that hose. If the engine idle increases, you got a split in that hose. Just a little tidbit to save you the hassle.
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From: Laguna Niguel, CA
Wow, talk about improvising. You took fuel line which is designed for outward pressure instead of vaccuum pressure, it's straight instead of the shaped part from MB and here's the toughest part you did you took off the shelf fuel line that is a single diameter and you made it fit the 2 different diameters the MB part is. Then, you say you still have some problems, hmm, yep, must be the $440 MAF, can't possibly be the $11 you skimped on using the wrong part.
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From: Charlotte, NC
2013 S550, CLS500, ‘03 SL500, “92 190E Sportline
Wow, talk about improvising. You took fuel line which is designed for outward pressure instead of vaccuum pressure, it's straight instead of the shaped part from MB and here's the toughest part you did you took off the shelf fuel line that is a single diameter and you made it fit the 2 different diameters the MB part is. Then, you say you still have some problems, hmm, yep, must be the $440 MAF, can't possibly be the $11 you skimped on using the wrong part.
Before we changed the hose, the car had a VERY rough idle,guzzled gas, and the vehicle shook violently from side to side constantly, unless it was off. As soon as we changed the hose all of that instantly stopped. So, yes, the culprit was the hose.
Now, since I have noticed the recent rough deceleration (mentioned above), I am assuming that this current problem may be the MAF, or it may be that the hose is kinked, since MB original hose is shaped differently...
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It's been mentioned before here - you might try pulling the plug to the MAF and see how the car runs. The car will now be running off programmed values (safe but not optimum, and open loop instead of closed-loop with the MAF sensor), rather than the MAF. If it still has the rough deceleration, it's not the MAF.
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From: Charlotte, NC
2013 S550, CLS500, ‘03 SL500, “92 190E Sportline
It's been mentioned before here - you might try pulling the plug to the MAF and see how the car runs. The car will now be running off programmed values (safe but not optimum, and open loop instead of closed-loop with the MAF sensor), rather than the MAF. If it still has the rough deceleration, it's not the MAF.
Better to clean MAF, or replace? What do you guys recommend?
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From: Laguna Niguel, CA
There's two scenarios, first like you said, you are forcing a straight tube into a complex shape, then apply vacuum for what it wasn't designed for so there's a very high probability that it's kinked or getting distorted during high vacuum (like when you let go of the gas pedal) to the point it's creating a blockage. The other possibility is a leak at one of the clamps as the factory hose has 2 diameters, that means your mechanic chose one diameter over the other on his fuel line and then improvised. My guess is he took the easy way out and improvised to fit the larger nipple, then he tightened the heck out of the hose clamp on the thinner nipple hoping that the engine wouldn't notice a little leak. Either of those thinks would do it, so if it were me, I would put the proper part in there as spending a lot of time diagnosing the problem by switching out $440 parts is not going to be fruitful.
As for the MAF, that's the easiest gizmo in that engine to troubleshoot. You can take the scientific approach and put a OBD2 scanner and see if you are getting the same readings a neighbor with a healthy engine is getting. Or you can do what I do, unplug it, if the car runs better without it, then it's the MAF, if it makes no difference or slightly worse, then it's not the MAF.
As for cleaning or replacing the MAF, I would just have your mechanic make one out of spare parts he has on his shelves, maybe radiator hose will work, haha!
As for the MAF, that's the easiest gizmo in that engine to troubleshoot. You can take the scientific approach and put a OBD2 scanner and see if you are getting the same readings a neighbor with a healthy engine is getting. Or you can do what I do, unplug it, if the car runs better without it, then it's the MAF, if it makes no difference or slightly worse, then it's not the MAF.
As for cleaning or replacing the MAF, I would just have your mechanic make one out of spare parts he has on his shelves, maybe radiator hose will work, haha!
Last edited by Buellwinkle; Feb 21, 2008 at 11:11 PM.
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Joined: Oct 2007
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From: Charlotte, NC
2013 S550, CLS500, ‘03 SL500, “92 190E Sportline
There's two scenarios, first like you said, you are forcing a straight tube into a complex shape, then apply vacuum for what it wasn't designed for so there's a very high probability that it's kinked or getting distorted during high vacuum (like when you let go of the gas pedal) to the point it's creating a blockage. The other possibility is a leak at one of the clamps as the factory hose has 2 diameters, that means your mechanic chose one diameter over the other on his fuel line and then improvised. My guess is he took the easy way out and improvised to fit the larger nipple, then he tightened the heck out of the hose clamp on the thinner nipple hoping that the engine wouldn't notice a little leak. Either of those thinks would do it, so if it were me, I would put the proper part in there as spending a lot of time diagnosing the problem by switching out $440 parts is not going to be fruitful.
As for the MAF, that's the easiest gizmo in that engine to troubleshoot. You can take the scientific approach and put a OBD2 scanner and see if you are getting the same readings a neighbor with a healthy engine is getting. Or you can do what I do, unplug it, if the car runs better without it, then it's the MAF, if it makes no difference or slightly worse, then it's not the MAF.
As for cleaning or replacing the MAF, I would just have your mechanic make one out of spare parts he has on his shelves, maybe radiator hose will work, haha!
As for the MAF, that's the easiest gizmo in that engine to troubleshoot. You can take the scientific approach and put a OBD2 scanner and see if you are getting the same readings a neighbor with a healthy engine is getting. Or you can do what I do, unplug it, if the car runs better without it, then it's the MAF, if it makes no difference or slightly worse, then it's not the MAF.
As for cleaning or replacing the MAF, I would just have your mechanic make one out of spare parts he has on his shelves, maybe radiator hose will work, haha!
But I definetely have been thinking that I should order the original hose and put that one in. I have to wake up early and do it, hopefully it will be easier than the first time!
I hope MB can mail me the hose, the nearest dealer is like over an hour away., hehe...
