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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 03-16-2010, 04:23 PM
dumbquestions dumbquestions is offline
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testing mass air sensor

anybody know the best test for maf sensor (correct result figures) ?

And any u pull it yards in florida with some e39 ?

Thanks
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  #2  
Old 03-16-2010, 06:14 PM
edjack edjack is online now
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I seem to recall that someone on this forum posted the resistance readings for the MAF sensor.
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  #3  
Old 03-16-2010, 06:16 PM
frhsfootball80 frhsfootball80 is offline
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How to test the MAFs yourself and How MAFs work

The MAFs are vital to the proper function of the S62 engine. The engine can never work better than its MAFs.

The MAFs (Mass AirFlow meters) are located in the M5 and Z8 air intake tubes. The MAFs report to the Engine Electronics (DME aka ECU) the amount of air that is drawn into the engine, and what temperature this air is. The DME uses this to calculate how much fuel to inject.

Vital as the MAFs are, those have to be _really_ bad before you actually get a stored fault-code.

The functional test by the BMW tester just tests the MAFs at idle with the car standing still. IMH experience that says absolutely nothing about how they perform at WOT (Wide Open Throttle).

I think there is an economical (warranty) reason why BMW does not want the MAF fault code to trigger as soon as the MAFs start to be less-than-perfect, rather than only when there is extremely poor MAF function.

MAFs typically last 50000 miles before getting so contaminated it affects S62 engine performance.

There are two methods to test the MAFs yourself:

Method A - using the instrument cluster of the car *********

Read post #11 in:

Gadget Freaks II: Fun you never knew you could have [secret menu]

Follow those instructions, and select the mode for fuel consumption per hour.
With the engine fully warmed up, drive several WOT (wide open throttle) accelerations. Notice the fuel flow per hour numbers. If everything is ok the numbers should increase continously to about 140 litres per hour at WOT at 7000 RPM. (donīt worry about bouncing into the rev-limiter)

The fuel-flow is directly proportional to the MAF reading reported to the Engine Electronics, so if the Fuel-flow is correct, the MAFs are most likely correct too.

To be able to compare your fuel-flow readings with other peopleīs readings,
you need to correct the data for temperature, barometric pressure and altitude. This is easy: look at the table attached at the bottom of this sheet.

Look up the two factors matching your temperature, barometric pressure and altitude. Then multiply the reading from the instrument cluster with both those factors. The result will match what the fuel flow number would have been at sea-level, +20 deg C and normal barometric pressure.

Method B - using an OBD-II scan-tool *******************

1. Get a graphing and data-logging OBD-II scantool. If you already have a laptop PC, it will cost you about US$ 100 to buy one. Worth every cent. (I use the one called "ISO" from www.obd-2.com which I am very pleased with)

2. Plug it into the car and go for a drive

3. Look at the graph for CLV (calculated load value). This is basically the MAF signal expressed in percent of the expected maximum at each RPM.
When you accelerate WOT this number should immediately go to 100% and stay there until you release the throttle or hit the rev-limiter .

4. If the CLV reading it is low at all RPMs, try new air filters.

5. If it is ok at low RPMs, but lower at higher RPMs, try the MAF cleaning procedure and the retest immediately. If this improves the numbers you know 100% there is (or if the cleaning was very successful used to be) a MAF problem. This does not say it is the only problem, but the car can never run better than its MAFs.

Symptoms of bad MAFs ************************

In degree of malfunction of the MAFs possible symptoms are:

High Lambda values at idle (lean air-fuel-mixture)
Engine hesitation at high RPM
Engine misfire at high RPM
Engine going into limp-home mode at high RPM

MAF cleaning procedure ************************

http://www.louv.tv/cars/m5/MAF/
(by m5board member Louv)

How the MAFs work ***************************

The MAFs have a non-heated temperature sensor and heated temperature sensor. The latter is made of a very thin wire of platinum metal. The wire is heated to about 200 deg C, and its temperature is continously monitored and the heating current is controlled so as to keep the wire at this temperature. The more air that passes the wire on its way into the engine, the more the wire will be cooled. The electrical current needed to maintain the sensor wire at 200 deg C, is directly proportional to the amount of air that passes it, and also depends on the temperature of the air (hence the non-heated temperature sensor).

The electrical current and the air temperature are measured, and the corresponding air-flow is calculated and reported to the engine electronics.

How MAFs clean themseves ***********

Once in a while the MAFs will run a very high electrical current for a few seconds through the platinum sensor wire, so the wire gets red-hot (1000 deg C). This burns off much of the contaminants, and probably help keep the MAFs working much longer between manual cleaning or replacment intervals.

How MAFs fail *********************

With time the MAF platinum-wire gets fouled with contaminants settling from the rapidly passing intake-air. These contaminants acts as thermal insulation on the wire. The effect is that the wire will not be cooled as much as it should by the air-flow, and thus reports too low air-flow to the engine electronics. The engine electronics in turn uses this too low air-flow number when calculating how much fuel to inject. The fuel injection will be to low, and the air-fuel mixture in the cylinders of the engine will be lean.

Many M5 owners have reported K&N oiled intake air filters to cause MAF contamination.

What to do if the L/H fuel flow numbers are low?
************************************

1. Have you corrected for altitude/barometric pressure/temperature and humidity?

2. Numbers still low? Most of the time, with a L/H reading very low, either the fuel pump/fuel pressure regulator and/or the MAFs are shot.

Most likely the MAFs.

To check the MAFs for severe contamination:

CHECKING MAFS
************

Either run the BMW DIS / GT-1 tester procedure for MAF testing at idle and inreceased idle RPM, or use this (IMHO far more accurate and reliable) procedure to measure MAF output voltages with engine off:

(Better still use both methods: road test L/H, and direct voltage. Then compare the results.)

MAF TESTING - DIRECT VOLTAGE METHOD
********************************

0. Remove tie-wraps holding wire protection tubing in place at the MAF connectors. Pull tube back and find the applicable wires. Connect to these using insulation piercing needle-and-hook type test leads(or just plain needle type test leads if you donīt mind risking to prick yourself).

Make ceratin to have the mulitmeter set to DC volts and that you have not connected to the AMPs connectors on it. (The signals you are connecting to go straight to the DME so be careful not to short-circit anything.)

1. Ignition on
2. Engine not running
3. On each MAF measure DC voltage between
pin 3 (ground, brown wire) and pin 5 (signal, yellow wire)
4. Reading should be 1.000 +- 0.040 V. The closer to 1.000 V the better. the dirtier the MAF the higher the voltage will be.
5. If reading in step 4 is off by more than 0.020 V then measure voltage between pin 3 and pin 4 (+5V reference from DME, yellow/green wire). This reading should be 5.000 +- 0.200 V.
6. If not check the battery voltage, and connect a charger if needed and redo the tests.

7. Put the tubing back in place and secure it with new black 2.5 mm wide tie-wraps. (Make sure you have narrow enough tie-wraps to fit on hand before cutting the old ones.) To avoid sharp edges, after the tie-wraps are in place cut the excess with a flush (one side only beveled) pair of cutting pliers.

If you donīt have that kind of cutters, just cut the tie-wraps with any sharp cutter and the file the sharp corners. Only takes a minute, and might save some of your blood next time you do something in that area on the engine compartment.

The reading in step 4 should be exactly 1/5 of the reading in step 5.

If this procedure gives a reading in step 4 that is outside tolerance the MAF is definitely contaminated or otherwise damaged.

FUEL PRESSURE
************

The other plausible possibility is the fuel pressure.

To measure the fuel pressure is very easy: he will need a BMW adapter for fuel pressure sensing (BMW special tool 13 5 220. This is a kit containing 13 5 221 and 13 5 222. This is common for all E39 5-series, so the dealer probably has it already) that connects to th efuel pressure regulator, and to the pressure test sensor on the DIS.

The procedure is very easy and is described in detail in TIS 13 31 029.

The thing to be aware of is that BMW states the fuel pressure as the difference between the absolute pressures in the fuel rail and in the intake tract (downstream of the throttle butterflies).

At idle the intake ports will be at -0.5 BAR. Just measure the atmosphere-relative pressure of the fuel-rail, and then add 0.5 BAR to get the reading relative to the intake ports.

In other words: hook the fuel test port up to the DIS, read the (athmosphere relative) pressure the normal way, and if it is 4.50 +- 0.05 BAR everything is fine so far.

Then disconnect the vacuum hose from the fuel pressure regulator, plug the hose, leave the fuel-regulator vacuum port open, start the engine again, and measure the fuel-rail pressure once more. It should now be 5.00 +- 0.05 BAR.

(The difference between these two readings is due to the vacuum pressure in the intake tract.)

BTW, this would be a good time to measure the vacuum too while you are at it as you have access to the hose anyway.

Warranty *************************

As the MAFs influence the air-fuel mixture and cause high Lambda values (lean mixture), it is possible to fail emissions testing due to non-perfect MAF sensors. When the vehicle fails emissions testing the Emissions Components Warranty may be applicable.

In the us see:

http://www.epa.gov/obd/warranties.htm

The mandatory warranty covers everthing relating to emissions for the first two years, and the OBD, ECU (DME in BMW language) and the Catalytic converters for eight years.

So in the US the MAFs are covered for at least 2 years by law, but not for eight years.

David
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  #4  
Old 03-16-2010, 07:07 PM
cn90 cn90 is offline
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The MAF is basically a hot wire suspended in air.
Revving engine ---> more air flows through ---> hot wire cools down ---> change in resistance ---> signal sending to ECU to inject more fuel to match with more air.
This is a very difficult device to test properly.
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  #5  
Old 03-16-2010, 08:04 PM
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Rustyzipper Rustyzipper is offline
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Holy Info Batman.... woow.. great post!!.. do you have carpal tunnel after that one??
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  #6  
Old 03-19-2010, 07:59 AM
540-S3 540-S3 is offline
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Post Expected MAF L/H Readings for All E39's

I have suggested several times that people use the cluster in testing their MAF, but I have yet to see anyone actually do it on this forum. The the M5 guys use it all the time to troubleshoot. One drawback to this method would be that many E39's are automatics, so getting the engine to redline may be a bit more difficult.

Using the method described by frhsfootball80, I have come up with L/H numbers for each of the e39 models. Be sure to correct for altitude/barometric pressure/temperature using this excel spreadsheet. Most of that information can be found using the weather information for your city.
Correction_for_peak_fuel_flow_data_ver_3.xls

528 1997-1998: 0.35 x 190 HP = 67 L/H
528 1999-2000: 0.35 x 193 HP = 68 L/H
525 2001-2002: 0.35 x 184 HP = 64 L/H
530 2001-2002: 0.35 x 225 HP = 79 L/H
540 1997-2002: 0.35 x 282 HP = 99 L/H

NOTE: Be sure to warm up your car before starting this test.

Post your numbers here and lets see how your MAF is functioning.
1997 540: The first time I ran this test the reading was 99 L/H adjusted. I just ran mine yesterday and I came up with 96.3 adjusted.
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Last edited by 540-S3; 03-19-2010 at 08:07 AM.
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  #7  
Old 05-21-2014, 03:27 AM
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bluebee bluebee is offline
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I was looking up the test for the MAF sensor for another user when I noticed we didn't have a canonical test thread for the MAF defined - so, doing a Bimmerfest search for MAF or mass air sensor test in the title, this seems to be the best so far "on bimmerfest".

Therefore, I'll make it the "canonical" thread on testing the MAF, which means that we'll update THIS thread as we move forward, for one-stop shopping.

It will take time, but, the starting point is a single thread.

See also these old threads, but some do NOT point to Bimmerfest (which means we can't update them).
- DIY for replacing (1) (2) (3) & cleaning your mass air flow (MAF) sensor (1) (2) (3) (4) (5) and how 'not' to clean your MAF (1) & buying a replacement MAF cheaper than the BMW MAF (RangeRover MAF) (VW MAF) (Hyundai MAF) & MAF resistance testing (1)
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See also: E39 Bestlinks & How to easily find what you need
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  #8  
Old 08-15-2014, 01:28 PM
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bluebee bluebee is offline
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More information on testing the MAF is here ...
> E39 (1997 - 2003) > P0015 P0171 p0173

Quote:
Originally Posted by johnstern View Post
Don't just throw a new MAF at it. You need to observe live data. Your MAF should be flowing about 3.99grams/second at idle.
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  #9  
Old 08-16-2014, 09:04 AM
gvelco gvelco is offline
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for mine air flow rate at idle is 3.92g/s.it should be up to 4g/s.
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Old 08-21-2014, 07:17 PM
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bluebee bluebee is offline
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This was posted today ...
> E39 (1997 - 2003) > Different MAF readings
Quote:
Originally Posted by gvelco View Post
when i connected scanner to my e39 525 reading there was 3.92 grams/sec,and for my friends 528(m52tu) it was 5.25 g/s.
how many x.gram/sec is correct?
also some measure maf condition with voltmeter,any DIY about that?
See also:
- MAF testing (1) & a DIY for replacing your MAF (1) (2) (3) & cleaning your mass air flow sensor (1) (2) (3) (4) (5) and how 'not' to clean your MAF (1) & buying a replacement MAF cheaper than the BMW MAF (RangeRover MAF) (VW MAF) (Hyundai MAF)
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
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  #11  
Old 01-26-2015, 05:01 AM
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sixpot_simon sixpot_simon is offline
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It'd be useful if, like the M5board guys, we can get a library of these measurements for each model. So here's my contribution:

530i: 70 L/h adjusted. Testing in 2nd gear with DSC off.
Engine is at 90k miles, running well* and no error codes. Raw measurement 70 L/h, temperature 20 degC, pressure 1016 mBar, altitude 40 metres. With DSC on, the L/h peaked at 6000 rpm, as is expected. But with DSC off, the reading was increasing all the way to the rev limit, which is a bit strange.

* However, if- as the theoretical target of 80 L/h indicates- there is an extra 14% power to be had, that's great news

Last edited by sixpot_simon; 01-26-2015 at 05:05 AM.
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  #12  
Old 01-26-2015, 05:31 AM
Burning2nd Burning2nd is online now
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yeah i was gonna say that... (not )

he took the time to explain it..

you can do a physical test with a meter
but your best and easiest way is just looking at the data thru a decent obd2 scanner
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  #13  
Old 01-26-2015, 03:24 PM
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sixpot_simon sixpot_simon is offline
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Quote:
Originally Posted by Burning2nd View Post
yeah i was gonna say that... (not )

he took the time to explain it..
I don't understand what you mean, sorry.
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Old 01-26-2015, 04:56 PM
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johnstern johnstern is offline
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There is some very interesting info in the posts above although it is a bit complicated/confusing.

The Bentley manual states that the MAF sends a signal to the ECU of .5 - 4.5 VDC. The lower voltage is that produced at idle. The higher the engine RPM, the higher the voltage. The I6 engine's MAF connector has 3 wires. The middle wire is the signal wire and can be accessed by back probing that wire. I don't know the configuration of the V8 MAF connector.

http://www.bimmerforums.com/forum/sh...-What-are-they

Auaq started the above linked thread. It explains MAF function. Beginning with post #7 he and I posted the results of testing MAF flow for his 530 (M54 engine) and my 528 (M52TU engine). No other forum members with different engines (M52, M62, M62TU and M54 as used in the 525) contributed data from their cars. The values in the tables are not definitive but instead represent a range as ambient temps, coolant temps, atmospheric pressures will change the readings. This fact can be seen in Auaq's two tables: the first taken on a warmer day than the second. gvelco's readings above seem to be in range-a few g/sec more or less don't indicate a failed MAF.

As an example I had a lean code. After making sure there were absolutely no vacuum leaks, I measured MAF flow at idle with an OBDII scanner that measured in lbs/hr. The MAF was reporting 23 lbs/hr. It should have been about 29 lbs/hr. The MAF was under reporting air flowing into the engine. Hence the ECU was not providing enough fuel for the air flowing into the engine-a lean condition. Replacing the MAF solved the problem.

But not knowing the air flow should not prevent MAF testing. The voltage produced at the signal wire would be enough to point to a failed MAF.

Last edited by johnstern; 01-26-2015 at 05:24 PM.
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Old 03-01-2015, 12:18 PM
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bluebee bluebee is offline
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This related question was asked today of how to test the MAS (aka MAF):
> E39 (1997 - 2003) > 2003 BMW 530i P2096
Quote:
Originally Posted by Softhands View Post
Johnstern Just read what you sent me; however I need more clarification since I am not real familiar with a DVM. First what do you mean by "back probe?" Also it would seem I would need to disconnect the connection to the MAF while the vehicle is idling to get the reading? I also went to a local parts place and their DVM are have several selections of DC volts for instance 10 Am and so on. Sorry for being ignorant about DVMs, but if you can provide me with more details it would help. One last question you state about .5 volts can you tell me + - range that is considered to be okay. Thanks.
Quote:
Originally Posted by johnstern View Post
It is actually quite easy to check your MAF if you have a digital volt meter. With the car idling you can measure the voltage generated by the MAF signal wire, the middle wire on the MAF connector. With the DVM set on DC volts back probe the center wire with the + lead and touch the - wire to a chassis ground. You should get a reading of about .5 volts.
EDIT: More info ...
Quote:
Originally Posted by johnstern View Post
When you back probe a connector, you insert the probe in the back side of the connector with that connector plugged in. In order to do this you must very carefully peel the protective rubber boot off the back side of the connector so you can insert the probe from the DVM in the place where the middle wire goes. If you look into that space, you'll see where the wire is attached to the connector. You need to touch the probe to that spot. When you're finished with the test, you carefully pull the rubber boot back into place.

I can't see the DVM you were looking at but you want to set the dial at "DC". 10 AM is for measuring amps, you want to measure volts. At idle, the signal (middle) wire should be about +.5 volts. That voltage will vary slightly based in altitude, temperature, barometric pressure. You want to measure the voltage with the car at operating temperature. That would be after a 1/2 hour drive because you want to have the oil warmed up as well as the coolant. Report back with your reading.

Maybe you could Google "how to use a DVM" so you could get more info.

I think it might better to have a knowledgeable shop test the MAF if you're not comfortable with the above. I can't imagine why the shop that did your engine swap is refusing to help you test your MAF. Maybe another knowledgeable BMW shop would be better.
Quote:
Originally Posted by Softhands View Post
Johnstern and or Alex5er I went to Autozone and borrowed their Digital Volt Meter and set it at 20. I also realized I had to removed the plastic cover on the MAF connector. My reading was .80 to .81 is an acceptable in regards to the range? Weird but not complaining the SES light went off once I got back in the car. Not sure what happen but still would like to know if the reading I got is within normal range as the light might might come back on. Thanks for your feedback.
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need

Last edited by bluebee; 03-01-2015 at 12:33 PM.
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