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Discussion Starter #1 (Edited)
Having a recurring issue with my 2005 330i. It keeps throwing the Fuel banks 1 and 2 Rich Codes (I believe P0171 and P0172 or some thing very close). Seems to be every so many miles I drive. Every time it throws the code and I go in a read it, there are four codes total showing. The first two have been thrown, the last two are 'Pending'.
My reader has the ability to do O2 sensor readings and testing. The Rich to Lean and Lean to Rich tests passed. The Voltage tests, however, did not. The Maximum voltage was a 0.450 instead of the listed 0.025 (the is what was listed as passing on the reader, no idea if it is accurate). The minimum voltage test had similar reading. Royally failed according to the reader.

I have not been able to find much on the meaning of the failed O2 sensor voltage tests. Is it worthwhile to replace O2 sensors or could it be something else?I know that the Rich and Lean codes are often blamed on the O2 sensors when that ends up not being the case, so I wanted more opinions before I tried that.

Thanks in advance!
 

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What tool are you using to read codes and run tests?

Can you post warm idle Fuel Trim values and Freeze Frame data.

If the engine really has Rich codes, it is usually a false positive and there is a sensor problem.

Have the O2 sensors been unplugged recently or any other major engine work been performed?

Do not knee jerk on O2 sensors, if they are bad, they rarely can trigger on Rich or Lean conditions. The ONLY time I see any O2 sensor codes that are valid is when the heater circuits fail in them.
 

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Discussion Starter #3 (Edited)
I don't have any freeze frame data currently, there is no active code. Once the pending codes become active I can get that.
I am using the Launch CRP 129 unit.
Below are warm idle fuel trim readings:
Short Term Fuel Trim Bank 1: Average -5.0%
Long Term Fuel Trim Bank 1: Average -26.0%
Short Term Fuel Trim Bank 2: Average -3.0%
Long Term Fuel Trim Bank 2: Average -26.0%

No major engine work performed recently, and the O2 sensors have not been touched.
This all started as follows:
After buying the car added some mileage additive and octane booster when fueling. Some work was done to the intake system (cleaning and diagnostics)
Rich codes were thrown on a longer drive shortly thereafter. After clearing the code, Rich codes have popped up ever since. No lack of performance or mileage in the car has been noticed. Nothing else appears out of the ordinary except the codes.
 

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How long have you had the car? You said no major engine work "recently".

This is really screwy with the STFT maxed out as well.

I would like to know what the MAF reading is at idle in park/neutral in Grams/Sec.

This is either a problem with the MAF way over reporting the air flow or something screwed up with the O2 sensors.

Possible O2 sensor wiring mixed up or non direct fit O2 sensors wired wrong?

http://forum.e46fanatics.com/showpost.php?p=16249570&postcount=27

http://forum.e46fanatics.com/showpost.php?p=16378620&postcount=26
 

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Discussion Starter #5
MAF reading at idle in Neutral fluctuates between 7 and 7.23g/sec
I also did a O2 sensor output test for both sensors and both are showing outputs of 0.6V and slightly above.

I have had the car since mid March of this year. I was told there was no major repairs ever needed or any issues, but we found some issues after buying the car. Battery and voltage issues as well as incompatible headlights (needed bixenons). Other than those issues, I have not done anything to the engine and mechanical parts of the car besides oil and fluid changes.
It is possible the sensors were replaced or taken out before I got the car.
 

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MAF reading at idle in Neutral fluctuates between 7 and 7.23g/sec
If this is the value at warm idle 600-700 RPM, then this is too high and this may be the primary reason you are seeing the Fuel Trims so negative. Typical MAF readings in Grams/Sec on these engines is usually around 3.5-4.5 Grams/Sec.

Rarely do MAF's age and Over Report, they usually Under Report. I have to assume that at some point an Asian counterfeit/clone MAF was installed. I would remove the MAF, take pictures and post them for review to include inlet and outlet side of the MAF and close up of the label/part number. Part of the problem is labels and plastic casting can easily be duplicated to look legitimate.

I also did a O2 sensor output test for both sensors and both are showing outputs of 0.6V and slightly above.
This may not be a useful test??? Usually I prefer to Log O2 sensor behavior, however, a constant Rich mixture would cause the O2 sensor Voltage to be on the high side of 0.45 Volts. So 0.6 Volts does seem to indicate a constant Rich mixture.
 

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Discussion Starter #7
Thank you for your help so far!
Being this is my first BMW, I am trying to get used to how everything works together and connects. There are so many parts an pieces on these cars that all work together in specific ways (this is coming from a person who had a '97 Subaru that had limited electronics).
Googling issues can only get you so far, doesn't help with really specific issues. That and I don't know some of the specifics to search for.

I will take a look at the MAF sensor and post some pictures, see what it looks like.

As for the O2 sensor output test, I wasn't sure if that would be useful or not. Just thought I would stick that in there and see if it was worth anything. Now that I know how the O2 can be affected like that, it makes much more sense.
 

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Discussion Starter #9
Sorry it took so long to get this! Been out of town quite a bit.
I will have pictures coming later today when I am able to get them on my computer.
In the meantime I was able to get the brand of the MAF and number.
Definitely not OEM or stock.
Brand: TPI (TrueParts Incorporated).
#: MAF1152
A142200010
 

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Sorry it took so long to get this! Been out of town quite a bit.
I will have pictures coming later today when I am able to get them on my computer.
In the meantime I was able to get the brand of the MAF and number.
Definitely not OEM or stock.
Brand: TPI (TrueParts Incorporated).
#: MAF1152
A142200010
Bingo! It's likely a cheap junk counterfeit Chinese aftermarket crappy MAF.

Does the engine run better or worse with that MAF unplugged?
 

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If the Fuel Trims move toward the correct range with the TPI MAF disconnected, then this is likely the problem.

Just because the MAF is not a Siemens/VDO MAF tells me this it highly suspect.
 

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Discussion Starter #12
Car physically runs fine with or without the MAF connected, just a matter of frequent codes. I will test this evening with the MAF disconnected to see if the readings move toward normal.
Is it possible the actual plug end on the car side is bad?
After putting the MAF in after getting the info in my last post, I took a road trip of a few hundred miles. Normally that would trigger the code. Nothing until I washed my car yesterday. As soon as the water hit it and started draining down the windshield , up came the code.
The code seems to take much longer to thow when I make sure the plug is in tightly.
 

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Discussion Starter #13 (Edited)
Took some fuel trim readings with the MAF unplugged.
short Term Fuel Trim Bank 1: -10% average
long Term Fuel Trim Bank 1: -22% average
Short Term Fuel Trim Bank 2: -9% average
Long Term Fuel Trim Bank 2: -25% average

Disconnecting the MAF didn't seem to help those readings much.

Reconnected the MAF (made sure the plug was in all the way) and got these readings (codes were cleared before the first tests above)

StST bank 1: -3% average
LTFT bank 1: -25% average
STFT bank 2: -0.9% average
LTFT bank 2: -26% average

MAF rate was averaging at 5.50 g/s
 

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My 2006 330cic (E46) MAF reading at idle is 4.6 g/s.

So if your MAF is reading 5.5 g/s this appears to be a bit high and is over reporting and will force the DME to increase the injector dwell time making the mixture richer.
 

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Discussion Starter #15
Everything I am seeing so far is pointing to the crappy MAF that was put in before I got it.
Is there anymore information I can gather that will point more definitely to the MAF or not?
I am thinking the next step I have is to get a new MAF (VDO from Bavarian Autosports) and see if that helps. I don't believe the cheap one currently in there is helping matters much.
It's an important part that I would rather make sure is running correctly than not.
Hopefully it stops the rich codes from throwing.
If not, we will at least have eliminated the MAF as the issue.
 

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Sounds like a good plan.

I hate to tell folks to replace MAF's because they are so hard to determine they are problems because most of the time they are only out by 10-20%, just enough to drive you nuts trying to sort out the problems.

Check for MAF pricing using this - http://www.bmwpnpc.com/
 

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Discussion Starter #17
Thank you for the program download! Helped quite a bit.
I have a new MAF coming. We will see how much that helps. Knock on wood it solves the issue.
I will post on here the results once I get it in and drive.
 

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Discussion Starter #18 (Edited)
So, an update on this issue. The new MAF arrived today and I was able to get it in the car. Cleared the previous codes and tested the car again at a warm idle. Found some interesting results.

MAF was much better between 4-5 g/s (opposed to 7 it was running at before).
STFT bank 1 was at 25% (positive this time instead of negative)
LTFT bank 1 was at -21%
STFT Bank 2 was around 23% (same as above, positive instead of negative)
LTFT bank 2 was around -20%

I reset the computer (unplugged the battery for about half and hour) and tested again with the same results.
The car idles between 500 and 1000 rpm. When in neutral, I increased the rpm to about 1500 to 2000. STFT in both banks dropped to below 15%, small change in LTFT. After releasing the gas, the STFT in both banks plummeted to below 5%, sometimes 0%, for a few seconds before shooting back up again.
I am going to test again after I drive the car more tomorrow to see if the results are any different.
I am also curious to see if it throws a code.

Any ideas on the strange results?
 

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Suggest driving the car for a few days to a week, normal driving and see if the Fuel Trim values start to "Adapt". Often this is the case where things take a while to adapt/adjust. Based on your Fuel Trims values this appears to be what is going on. Disconnecting the battery will not "clear the Adaptations", matter of fact it will not do much of anything unless it is disconnected for weeks. Software is required for resetting the Adaptations, or you just need to drive the car and see if the Fuel Trims start to fall in line where expected.

Additionally there may be multiple problems and you have to chip away at them one at a time.

Log files are the best approach because there can often be data points that are missed when passing info along.

Also make sure things like the O2 sensors are in fact connected properly, the wiring can easily be mixed up and cause all sorts of headaches and strange problems.
 
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