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BMW E39 Mass Air Flow Sensor Replacement
 
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Pelican Technical Article:

BMW E39 Mass Air Flow Sensor Replacement

Kerry Jonsson

Time:

1 hour1 hr

Tab:

$100

Talent:

**

Tools:

Flathead screwdriver, 10mm socket and ratchet

Applicable Models:

BMW 525i Sedan/Wagon (2001-03)
BMW 528i Sedan/Wagon (1997-00)
BMW 530i Sedan (2001-03)
BMW 540i Sedan/Wagon (1997-03)

Parts Required:

Mass air flow sensor, engine air filter

Hot Tip:

Work with a cool engine. Clear engine fault codes when done

Performance Gain:

Car will run well.

Complementary Modification:

Replace engine air filter, inspect intake air ducts for cracks or dry rot.

The mass air flow sensor monitors air flow into the engine and creates a digital signal for the DME. Mass air flow sensors accuracy skews over time and can lead to fault codes or drivability problems. When replacing inspect the rubber intake air ducts for cracks or dry rot. If intake air ducts are faulty, replace them first and see if the problem you are having is remedied. An un-metered air leak downstream of the mass air flow sensor will set codes similar to a faulty mass air flow sensor.

Models with 6-cylinder engine:

There are two different style mass airflow sensors on 6-cylinder equipped models depending on engine type. I separated the procedures for you, even though they are similar. This will help to avoid any confusion.

Early 6-cylinder:

Early 6-cylinder models have a longer mass airflow sensor (green arrow) body and utilize a screw-in type electrical connector.
Figure 1

Early 6-cylinder models have a longer mass airflow sensor (green arrow) body and utilize a screw-in type electrical connector. Always inspect and replace any cracked air intake ducts when servicing your mass airflow sensor (yellow arrow)

Disconnect the mass airflow sensor electrical connector by rotating electrical connector (green arrow) counterclockwise and pulling it straight off.
Figure 2

Disconnect the mass airflow sensor electrical connector by rotating electrical connector (green arrow) counterclockwise and pulling it straight off.

Next, using a flathead screwdriver, loosen the mass airflow sensor clamp.
Figure 3

Next, using a flathead screwdriver, loosen the mass airflow sensor clamp.

Then unclip the two spring clips that hold the mass air flow sensor into the air filter housing lid.
Figure 4

Then unclip the two spring clips that hold the mass air flow sensor into the air filter housing lid. Use a flathead screwdriver and lever away from the sensor.

Pull the mass airflow sensor out of the intake air duct, then slide out of the air filter housing.
Figure 5

Pull the mass airflow sensor out of the intake air duct, then slide out of the air filter housing.

If O-ring (green arrow) gives you a hard time going in, apply a small amount of dish soap to O-ring, it will slide right in and the soap will not damage O-ring.
Figure 6

If O-ring (green arrow) gives you a hard time going in, apply a small amount of dish soap to O-ring, it will slide right in and the soap will not damage O-ring. Install new mass airflow sensor into air filter housing. Secure retaining clips and tighten hose clamp. Then reconnect electrical connector. Take vehicle for a test drive, then recheck your intake air duct connections.

Late 6-cylinder:
Late 6-cylinder models have a shorter mass air flow sensor (green arrow) body and utilize a push-in type electrical connector.
Figure 7

Late 6-cylinder models have a shorter mass air flow sensor (green arrow) body and utilize a push-in type electrical connector. Always inspect and replace any cracked air intake ducts when servicing your mass airflow sensor (yellow arrow)

Disconnect the mass airflow sensor electrical connector by pressing the wire release tab and pulling it straight off.
Figure 8

Disconnect the mass airflow sensor electrical connector by pressing the wire release tab and pulling it straight off.

Next, using a flathead screwdriver, loosen the mass airflow sensor clamp (green arrow).
Figure 9

Next, using a flathead screwdriver, loosen the mass airflow sensor clamp (green arrow). Then unclip the two spring clips (yellow arrow) that hold the mass airflow sensor into the air filter housing lid. Use a flathead screwdriver and lever away from the sensor. Pull the mass airflow sensor out of the intake air duct, then slide out of the air filter housing.

If O-ring (green arrow) gives you a hard time going in, apply a small amount of dish soap to O-ring, it will slide right in and the soap will not damage O-ring.
Figure 10

If O-ring (green arrow) gives you a hard time going in, apply a small amount of dish soap to O-ring, it will slide right in and the soap will not damage O-ring. Install new mass airflow sensor into air filter housing.

Models with 8-cylinder engine:
Using a flathead screwdriver, unclip all four air filter housing retaining clips.
Figure 11

Using a flathead screwdriver, unclip all four air filter housing retaining clips. (green arrows).

Once you release all the clips, unscrew the mass air flow sensor electrical connector (green arrow) by rotating it counterclockwise and pulling it off sensor.
Figure 12

Once you release all the clips, unscrew the mass air flow sensor electrical connector (green arrow) by rotating it counterclockwise and pulling it off sensor.

Using a flathead screwdriver, unclip the top spring clip (green arrow) that holds the mass airflow sensor into the air filter housing lid.
Figure 13

Using a flathead screwdriver, unclip the top spring clip (green arrow) that holds the mass airflow sensor into the air filter housing lid.

Using a flathead screwdriver, unclip the lower spring clip (green arrow) that holds the mass airflow sensor into the air filter housing lid.
Figure 14

Using a flathead screwdriver, unclip the lower spring clip (green arrow) that holds the mass airflow sensor into the air filter housing lid.

Remove the air filter housing lid from the mass air flow sensor.
Figure 15

Remove the air filter housing lid from the mass air flow sensor. Lift it and pull them apart.

Loosen air flow meter clamp (green arrow), then disconnect air flow meter from duct and remove from engine.
Figure 16

Loosen air flow meter clamp (green arrow), then disconnect air flow meter from duct and remove from engine. On my vehicle, there was a zip tie holding the duct on. This is not correct and could cause an unmetered air leak. I replaced the zip tie with a new hose clamp.

Once mass air flow meter is removed, transfer the seal (green arrow) over to the new sensor.
Figure 17

Once mass air flow meter is removed, transfer the seal (green arrow) over to the new sensor.

Check that O-ring is in good shape and not worn or swollen.
Figure 18

Check that O-ring is in good shape and not worn or swollen. Replace if needed (green arrow) Install new mass airflow sensor into air filter housing. If O-ring gives you a hard time going in, apply a small amount of dish soap to O-ring, it will slide right in and the soap will not damage O-ring. Install air filter housing lid into vehicle in reverse order of removal. Take vehicle for a test drive, then recheck your intake air duct connections.

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Comments and Suggestions:
Phetole Comments: Good day. How much is shipping of parts to South Africa
February 12, 2015
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help figure it out. - Nick at Pelican Parts  
Conrad Comments: 1999 BMW 528IT,170,000 miles. Engine has new Bosch plugs, air filter and Two, O2 sensors. The car starts and runs well with no engine alarms or lights. Neverthe less the mileage is about 19 mpg, much less than previously. What are your suggestions? Please advise. Thank you
Conrad
April 5, 2014
  Followup from the Pelican Staff: I would check fuel trim using a BMW scan tool. You will be able to see when fuel control is skewed. That will give you direction when diagnosing. - Nick at Pelican Parts  

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