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Discussion Starter · #1 ·
Hi All,
I haven't been able to find anything relating to testing a MAF on the e39 3.0L engines so I decided to take some readings while replacing mine. My 2001 530i Sport w/60k miles would stall every once in a while and also had occasional sluggishness. I checked for vacuum/air leaks, checked electrical, etc. I cleaned the original MAF once and it seemed to do good for a couple of months, but decided to replace the unit. Got my replacement OEM Siemens VDO part today. Everything seems fine now so I'll keep tabs on the performance and note the results and any changes.

I'm not sure of the proper testing method so I used my test meter and took some Ohm readings from the two units. If anyone knows more about testing these specific MAFs, please share. Here are my results:

BMW Air Flow Meter/MAF Sensor Testing with Ohm Meter

Siemens/VDO for e39, 3.0L, 530i Sport (2001 model year, mfg. 02/01)
BMW Part #13621438871

(Left to Right following airflow arrow ---->)

Pins are labeled on top of the sensor electrical connector:

Pin 3 Pin 2 Pin 1
----> ----> ----> ----> ---->

New OEM Sensor:

Test #1:
Pin 3 (red lead) + Pin 2 (black lead) = 10.00 M Ohms

Test #2:
Pin 2 (black lead) + Pin 1 (red lead) = 16.62 K Ohms

Test #3:
Pin 3 (black lead) + Pin 1 (red lead) = 3.13 M Ohms

Test #4:
Pin 3 (red lead) + Pin 1 (black lead) = 10.10 M Ohms


Original Used Sensor:

Test #1:
Pin 3 (red lead) + Pin 2 (black lead) = 7.17 M Ohms

Test #2:
Pin 2 (black lead) + Pin 1 (red lead) = 16.72 K Ohms

Test #3:
Pin 3 (black lead) + Pin 1 (red lead) = 2.88 M Ohms

Test #4:
Pin 3 (red lead) + Pin 1 (black lead) = 7.25 M Ohms
 

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ok, so ur getting a little less resistance on ur new sensor if i'm reading ur post correctly...

but i think the main purpose of testing the MAF w/ a multimeter is with use of the throttle as well - i think the voltage from the sensor is supposed to varry a certain amount around 5volts?

(i'm not positive, but i remember reading that somewhere, wish i cud remember for ya bro)
 

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Discussion Starter · #4 ·
Thanks for the link, but I'm not sure method #1 will work on my car. The 2001+ 3.0L engines use electronic throttle control so I don't think I can rotate the throttle plate by hand like he suggests

FYI, I did just go for a 20-mile test drive and there is a very noticeable difference in both normal driving as well as performance driving! Very smooth all around and response off the line is greatly improved.
 

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did some searching and found my source - good ol' Ryan from here on the boards.

http://www.bimmerfest.com/forums/showthread.php?t=296559&highlight=maf+test
I was just going to chime in:D.

Unplug the maf and check for a 5v reference with the key on engine off. This will verify that the harness is operating.

With the harnes plugged in, you can backprobe the 5v reference wire at idle. It should be reading near .5v. Then give the car some gas. As the rpm increases, the voltage should increase. to as high as 4.7v. You must do this with the vehicle running, because the maf in the e39 is a hot film type. This means that the DME applies 12 volts to the sensor and heats it to 200 degrees above ambient temperature. This is where the 5v signal wire comes into play. As you drive, the more air you have drawn in by manifold vacuum, the cooler the sensor gets. The signal wire is there purely for the DME to monitor and see how much more current is required to keep the sensor at 200 degrees above ambient temp. The more current the DME sees needed, the more air it knows is coming in. Then it can make injector pulse width adjustments accordingly.
 

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Thanks for the link, but I'm not sure method #1 will work on my car. The 2001+ 3.0L engines use electronic throttle control so I don't think I can rotate the throttle plate by hand like he suggests
You can use that method to test the TPS, but not the maf. You need the car running to test the maf. But, whether you have drive by wire or throttle cables, you can still test the tps with the key on engine off. The TPS is a three wire variable resistor called a potentiometer. As you rotate the throttle plate via accelerator inputs, you vary the amount of voltage in the resistor. The DME recognizes these changes and calculates how far open the throttle plate is. So, to test, turn the key on with the engine off, backprobe the signal wire. You should get .5v at idle and 4.7v at WOT. It should be a smooth increase from .5v to 4.7v without interruption. You can also test the TPS by using an ohmmeter, but I don't have the values offhand. Just remember, all sensors work off of a 5v reference.
 

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Discussion Starter · #7 ·
Just a quick update on the MAF replacement. Its been over 5 days of constant driving and everything with the car is great. No problems or hints of the issues that were around before the MAF replacement. The engine is much smoother and responsive than before. Just wanted to let you all know!
 

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FYI, I did just go for a 20-mile test drive and there is a very noticeable difference in both normal driving as well as performance driving! Very smooth all around and response off the line is greatly improved.
Just a quick update on the MAF replacement. Its been over 5 days of constant driving and everything with the car is great. No problems or hints of the issues that were around before the MAF replacement. The engine is much smoother and responsive than before. Just wanted to let you all know!
Hey Chris,

I see you got to install that BMW Siemens VDO MAF sensor you bought from me, huh? I agree with all your impressions above. I experienced the same drastic improvements in smoothness, everyday driveability, acceleration and even fuel consumption.

I really recommend changing the MAF to anyone who has more than 70K miles on their car. It made a huge difference for me, and sounds like Chris has had similarly positive results. I still have 2 sensors left available for sale. I purchased 5 to get a better price, installed one on my car and one on my GF's car. I posted a thread about this a couple of weeks ago. There is a link at the bottom. Anyone who is interested in replacing their MAF on the 3.0L I6, please feel free to PM me.

http://www.bimmerfest.com/forums/showthread.php?t=299433&highlight=
 
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