: Another P0171 Thread



2001sport
09-19-06, 11:31 PM
My wife's Cat threw P0171 back in February, which resolved by changing the fuel filter. She drove the car for another 2 months and since early May and the birth of our son, the car has seen very little use. Last week, the CEL came on, and sure enough, it's our friend P0171 again. Based on the large number of threads I've read here, reason would dictate the problem is the MAF sensor. However, before I decide to spend the $115+ shipping to buy a new one, I have a few questions:

- has anyone with P0171 successfully resolved the problem by cleaning the MAF rather than replacing it?

- considering that the fuel filter is basically new, should I rule that out as a potential problem, or is it likely there's a problem with either the new filter or the installation? (I'm trying to avoid wasting time taking the car back to the mechanic that installed it.)

Thanks in advance.

2001sport
09-21-06, 01:22 PM
Quick update without any progress. Upon further research, the MAF was already cleaned by the mechanic when they replaced the fuel filter. (I found that out by reading one of my old posts here. Nice memory. :crybaby:) I could try cleaning it (again) myself, but am now wondering:

- will fuel injector cleaner possibly help, which was suggested by someone in a previous thread, as well as the kid at AutoZone?

- will it hurt to continue driving the car? In other words, if the MAF sensor is bad, is that simply causing the CEL to go on, or can a bad sensor actually have a negative impact on the car's performance, or even lead to other problems? So far, it seems to run fine.

- has anyone ever had P0171 for other reasons, or should I just break down and go buy a new MAF sensor?

wamanning
09-23-06, 12:55 PM
- has anyone with P0171 successfully resolved the problem by cleaning the MAF rather than replacing it?


i did. but it worked for maybe a month. maybe. then the CE light came back on w/ same code. so i fitted a new MAF and all is good since spring-time.

walter

guardian
09-24-06, 05:27 PM
i did. but it worked for maybe a month. maybe. then the CE light came back on w/ same code. so i fitted a new MAF and all is good since spring-time.

walter

Agreed.

My instinct is to clean because of the expense of replacement. But it's a wrong instinct, I think, and replacement is the way to go.

The only exception would be if a proper and effective cleaning solvent exists/could be identified. If it does, I surely do not know what it is. My gut says proper and effective cleaning of these hot wires, when they are cold, is a tough nut to crack. Just a guess, but the impurities may be trapped at a molecular level, if that's the right way to say it; trapped in a non-conventional manner anyway. Effective cleaning, if it can be done at all, likely would require knowledge of both metallurgy and chemistry. That's not me.:tisk:

Warez
09-24-06, 08:11 PM
The poblem is not dirt on the MAF elements, these Bosch MAF's are just plain junk. Various BMW's and VW's use a very similar type and they fail all the time as well. Just replace it.

It is only $114 are rockauto.com

2001sport
10-20-06, 02:16 PM
Thanks for the input, everyone. I went ahead and ordered the MAF from Rockauto, fitted it and the CEL is still on. If the problem was indeed a bad MAF, would the CEL go off on its own, or does the ECU need reset. If the latter, how do I reset it? (I've read some people just disconnect the battery, but I'm not sure exactly how to do that and I want to be safe.)

2001sport
10-21-06, 02:13 AM
ok, forget the previous post. I disconnected the battery (black terminals only) for about 10 minutes, then reconnected, but am still getting the CEL. Since it seems I may have just thrown away $120 on a MAF sensor, does anyone have any other suggestions before I give up and hand the car over to my local mechanic?

Zorb750
10-21-06, 11:06 AM
The poblem is not dirt on the MAF elements, these Bosch MAF's are just plain junk. Various BMW's and VW's use a very similar type and they fail all the time as well. Just replace it.

It is only $114 are rockauto.com

BMW uses a hot film MAF, the Catera uses a heated wire MAF as I recall.

BMW sensors almost never fail, they can nearly always be cleaned (just use alcohol 91 or 99%, according to BMW TIS)

Warez
10-21-06, 06:41 PM
BMW uses a hot film MAF, the Catera uses a heated wire MAF as I recall.

BMW sensors almost never fail, they can nearly always be cleaned (just use alcohol 91 or 99%, according to BMW TIS)

Which models are you talking about?

I know that the sensors used by models with the I6 and V12's were virtually identical to our Bosch MAF's (they are not made by BMW). Most of the electronics on BMW's as with our cars are made by Bosch and are evry failure prone.

Contrary to popular belief, BMW's are not all that reliable.

Elo
10-23-06, 05:56 PM
About 2 weeks ago, my 2000 Cat threw out the P1511 code. I took it to Advanced Auto Parts and they gave me a printout of the code and cleared it for me... Light has yet to come back on (aside from at startup)...

So if your problem is clearing the code, try taking it to Advanced Auto Parts (if you have one around you)... They can read out the code/clear it and will do it for free...

-Elo

Serobin88
10-24-06, 10:03 PM
What is a MAF?

2001sport
10-28-06, 11:40 AM
Mass Air Flow sensor.

2001sport
10-28-06, 11:52 AM
Thanks, Elo. We have a few Advanced Auto Parts around here, but none of them will clear the code. The response I keep getting from these stores (including AAP, AutoZone, Murray's) is that they aren't allowed to do this anymore. I'll try disconnecting the battery again, but if that doesn't work I guess it's off to the shop...

2001sport
10-29-06, 12:00 AM
Success! I think I might not have completely disconnected the terminal last time, but the CEL finally cleared. I've already had a handful of starts without it coming back on, so it looks like the new MAF did the trick. Thanks for everybody's help along the way! :)

OffThaHorseCEO
10-31-06, 05:18 PM
did it run weird with the bad maf, like was it jittery or jumpy or shaky or anything?

im getting the p0171 AND p0174 (left and right banks lean) and im tryin to find formulate a plan of attack here

Warez
11-01-06, 02:45 AM
It may run rough until the engine warms up and the PCM begins reading the O2's.

I bet your problem is a MAF as well.

klm
11-01-06, 10:57 AM
I had the same issue. Both banks lean. MAF fixed it.
The service manual trouble shooting guide points you in all kinds of other directions, but for me, and dozens on this forum who helped me decide, the MAF does the trick more often than not.
Good luck.

whoareyou4
11-01-06, 12:51 PM
I have the same code I also have P0174, so both my left and right banks are lean.
Alldata says to check for vacum leaks, check the pcv system, and check the Secondary Air Injection system, check into fuel delivery.
Aldata says to check the oil filler cap and dipstick make sure they are tight

So there is lots of stuff to check.

What about oxygenated fuels? Can that cause a problem?

2001sport
11-01-06, 10:54 PM
did it run weird with the bad maf, like was it jittery or jumpy or shaky or anything?no noticeable difference, to be honest. that's one of the reasons i was so hesitant to spend the money on the sensor at first, but i'm glad i did now, especially considering how much my mechanic wanted to diagnose and fix the problem...