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Discussion Starter · #1 ·
Hey, I was just wondering if anyone has any insight on tracking down an electrical issue. Currently, I have a MAF low voltage and coolant temperature implausible code. On my OBD tool, the MAF reading is about 7 g/s at idle (950 rpm), which I believe is a high? I haven't been able to find any info on an M3 specific average value though. I've also had my right side door lock not open with a key press and the right side headlight intermittently go out. I haven't had the latter two happen recently, though. I just cleaned ground point X166 (under the right headlight) and where the battery connects to ground. If it makes any difference, I recently replaced my brake booster to get rid of a vacuum leak that I had been living with for a while. The MAF only started acting up after clearing the lean codes for that.

Any help would be appreciated. I've heard that a lot of people aren't able to get rid of a P0102 by just replacing the MAF, so I wanted to see if you all have any insight. Thanks.
 

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Yes, that MAF reading is too high. It should be under 5 grams/second. As I remember my old 3l M54 would read about 4grams/second at idle.

Do you have a digital volt meter? Check the voltage at the jumper post under the hood under the red plastic cover. Use the engine as ground. Report back your voltages when the:
  • ignition switch is in the accessory position
  • ignition switch is in the run position with the engine off
  • engine idling
  • engine revving at 2000rpm.

These cars are rolling computers and whacky voltages cause whacky issues.
 

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2004 330Ci 115k miles
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Post each fault code along with its text description.

One can quickly gain knowledge on these problems by searching the forums to see what others have done to troubleshoot.
I would prioritize the issues in this order, based mainly on safety, then focus on one at a time.
  1. MAF
  2. Right headlight
  3. Right door lock
The MAF value of 7 g/s at 950 RPM does sound a little low. I don’t recall the typical S54 idle speed, but 950 RPM sounds high.

Does this M3 have adaptive xenon headlights, or the simple halogens?

Is your GM5 module coded to unlock both doors on first remote button press?
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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A 3.2L engine should be drawing just a bit less than 4 g/s at around 700 rpm idle. At 950 rpm, it should be around 5 to 5.5 g/s. So, 7 g/s is a little high.

  • Confirm your code numbers and descriptions as suggested.
  • Also provide the Short Term and Long Term fuel trims from each bank at hot idle.
 

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Discussion Starter · #5 ·
The codes I'm getting are

Current fault - P0102 - Powertrain: Mass or Volume Air Flow Circuit Low Input
INPA reads this as 44 Luftmassenmesser 1

Pending fault- P0128 - Powertrain: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
INPA reads this as 105 Plausibilisierung Motortemperatur

Oh, and the right headlight just went out again, and it is a xenon. Right side lock is working though. It did just rain yesterday, and I remember reading a thread on here a while ago about someone who was having electrical issues pop up just after rain, but I can't seem to find it again. That's why I'm thinking it all has to do with some wiring somewhere, possibly a bad ground.

I'll do the fuel trim and voltage tests suggested tomorrow when I go and grab a multimeter.
 

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Discussion Starter · #6 ·
Alright, here's what I've got. Sorry it took a few days, I couldn't get a hold of a multimeter until now. I also just replaced the drive belt, belt tensioner, and idler pulley (was having belt squeak anyways) hoping that might help things, but no dice.

Voltages:
Position 1: 12.89 V
Position 2: 12.66 V
Idle: 14.12 V
I wasn't able to rev it and check the voltage. If it's real important, I can get a friend to help me out later.

INPA info:
I just took a couple screenshots when I was idling in a fast food line. Not sure how to read fuel trims, but I'm pretty sure the Analog 2 screen has the info for that?
Rectangle Font Slope Parallel Screenshot

Rectangle Font Parallel Slope Screenshot

Font Parallel Number Screenshot Rectangle


Thanks in advance for any help, hope you all can make something of this.
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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Fault Code 41 (Dec) has 2 different P Codes related to it in the MS S54 DME:
  • P0102, Mass or volume air flow circuit low input
  • P0103, Mass or volume air flow circuit high input
Both the MAF values in the INPA screen shot and in the Fault code freeze frame data show an over reporting MAF for the recorded Rev's. An Over Reporting MAF causes Rich (negative) fuel trims.
  • Multipicative are the long term fuel trims equivalent in INPA. Yours are 1%, which is spot on.
  • Additive are the low load fuel trims in INPA. They are measured in ms of injection pulse. Yours are showing a negative number which indicated that the DME is controlling a rich condition.
My guess on the above data is that you have a duff MAF that is over reporting. But that is only based on a couple of data points, both at idle.

If you could get me a scanner log file, I can give you a test to run and then analyse the log for you, to see what it shows.

You have two options for getting the log file:
  • Load TestO onto your laptop. It runs on the same communication bus as INPA. Record a log of RPM, MAF flow in kg/hour (not Volts), additive for both banks and mulitpicative for both banks. Get TestO here: Diagnostic program with realtime graph view
  • Set up OBD Fusion on your smart device and buy the OBD2 EML327 donkle. Less than $50 invested. Read the following link and set it as per the PDF instructions. OBD Fusion
I can work with both TestO and OBD Fusion logs. OBD Fusion would be the preference.

While I have done lots of BMW MAF checks. This will be the first S54 MAF check, so my models may be a little out of calibration. I have to do the calibration at some time, so I'm interested in seeing your log.
 

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Discussion Starter · #9 ·
Alright, I've got a new (to me) MAF sensor on the way. Even if it doesn't go the distance, it'll at least help me figure out whether this a problem with the sensor itself or some wiring somewhere.

As for testing, it's looking like I'm gonna be blocked in pretty much all day today, but I'll hopefully be able to get some numbers tomorrow. I've downloaded TestO, but I could also buy OBD Fusion if that works better. I think I've got some leftover Google Play credit laying around. My current scanner is this guy that I got with my head unit, and it looks like that should be ELM327 compatible? It runs fine with Torque, so I assume that means it's all good.
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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Yes, that EML327 will work with OBD Fusion.

If you use TestO, it's not that intuitive out of the box:
  • Most descriptions of the data points are in German. Google translate fixes that.
  • Select the DME and then double clip on the data point you want. This will open a little graph box.
  • There will be a list of data streams associated with the data point. You have to select one in order to get the graph plotting data. It's usually the bottom check box. The one with "Werths" in the description.
  • Once you have selected all the data points you want to log, you need to turn the log on. It's in the Menus. Don't have TestO with me right now, so going by memory. Click on the logging in the menu. this opens a dialogue box showing you all the data points you have running. You must select 1, then hit the "start" button at the bottom of the dialogue box. If you don't select at least 1 data point, you will log a whole lot of no data.
  • hit the "stop" button at the bottom of the dialogue box to turn the logging off.

OBD Fusion is a lot easier.

The MAF test is called the Rev-Rise Test.

Run your normal OBD Fusion log. Hot engine and Cat’s, stationary car. The test is best done just after a drive. Slowly raise the rev's of the engine up from idle to around 3,000 rpm. I mean slowly. It should take you 3-4 minutes to do this test.

It takes some skill to do this test due to the lightly loaded engine. A little throttle change results in a large rev change. Don’t run up and down the rev range getting used to the control. If you stuff up the first part of the test getting used to controlling the small rev changes, then redo the test.

Looking forward to seeing your results.
 

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Hey, I was just wondering if anyone has any insight on tracking down an electrical issue. Currently, I have a MAF low voltage and coolant temperature implausible code. On my OBD tool, the MAF reading is about 7 g/s at idle (950 rpm), which I believe is a high? I haven't been able to find any info on an M3 specific average value though. I've also had my right side door lock not open with a key press and the right side headlight intermittently go out. I haven't had the latter two happen recently, though. I just cleaned ground point X166 (under the right headlight) and where the battery connects to ground. If it makes any difference, I recently replaced my brake booster to get rid of a vacuum leak that I had been living with for a while. The MAF only started acting up after clearing the lean codes for that.

Any help would be appreciated. I've heard that a lot of people aren't able to get rid of a P0102 by just replacing the MAF, so I wanted to see if you all have any insight. Thanks.
950 RPM idle? That's too high. Should be around 700 RPM. And if your idle speed is too high your MAF reading is also going to be too high.

Anyway.
I have a 2.2L M54 and the MAF reading at 700 RPM idle is 10 Kg/Hr ( 2.7 g/s).
If yours is 2.2L that should be 3.7 g/s at 950 RPM.
If yours is 3L that should be 5 g/s at 950 RPM.

I think you need to sort out your idle speed (dirty ICV?) and clean the MAF using the correct MAF cleaning solvent spray.
Then check it again.
 

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Discussion Starter · #12 ·
I think I got OBD Fusion figured out. Here's the file. Sorry it's only 2 minutes, if the data set is too incomplete, let me know. I just got the new MAF sensor in, so I'll try to get you the data from that soon. It seems to have fixed the fault code, but I haven't driven it for an extended duration yet so we'll see what happens.
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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Yes it looks like your MAF is the problem:
  • Over Reporting MAF a low rpm causing Rich (negative) fuel trims.
  • At about 1,800 rpm the MAF swaps over to being an under reporting MAF with associated lean (positive) fuel trims.
  • The lean trims get worse the more the MAF under reports with increasing rpm.

Human body Rectangle Slope Plot Font


Time Invested
This took 3/4 of an hour to spread sheet the log and right up this post.
 
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