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Cooper S Mass Air Flow Sensor Replacement
 
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Pelican Technical Article:

Cooper S Mass Air Flow Sensor Replacement

Nick Czerula

Time:

1 hour1 hr

Tab:

$500

Talent:

**

Tools:

T25 Torx driver

Applicable Models:

R56 MINI Cooper S Hatchback (2007-11)

Parts Required:

Mass airflow 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

The MINI R56 digital engine management (DME) systems use a hot-film mass airflow sensor, installed between the air filter housing and the intake manifold, to monitor air flow into the engine intake. Inside the sensor, there is a thin metal film, which is maintained at a constant temperature via electrical current from the ECM. As ambient intake air flows over the film, it is cooled down and therefore additional current is needed to maintain its constant temperature. The ECM monitors this additional current to determine the mass of the incoming air and to adjust fuel supply accordingly. Note that as the temperature of ambient air increases its volume expands. Since the air flow sensor hot film monitors heat-loss to the passing air, it automatically adjusts for the increased volume (= lower density) of the incoming air. The HFM6 style sensor sends a digital mass airflow and temperature signal to the DME. For more information, see our tech article on mass airflow sensor testing.

Mass airflow sensors accuracy skews over time and can lead to fault codes or drivability problems. When replacing, inspect the plastic intake air ducts for cracks or dry rot. If the 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 airflow sensor will set codes similar to a faulty mass airflow sensor. When you suspect a mass airflow sensor as the culprit for setting a fuel trim fault code, check when the fault code was set. You can do this using OBD II freeze frame data. Normally, a vacuum leak would set a fuel trim fault code at idle or very low engine RPMs. A mass airflow meter would usually set a fault code when you are driving, or at a higher RPM. You can check your fault code freeze frame data using an OBD II scan tool, similar to how you would check for fault codes.

In this tech article I will show you how to replace the mass airflow sensor on MINI R56 models with 4-cylinder turbocharged engines.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Turn the engine OFF and remove the remote key from the vehicle interior or the remote key slot.

The mass airflow sensor (green arrow) is located at the air filter housing (red arrow) outlet on the left side of the engine.
Figure 1

The mass airflow sensor (green arrow) is located at the air filter housing (red arrow) outlet on the left side of the engine.

Disconnect the mass airflow sensor electrical connector by pressing the release tab (red arrow) and pulling the connector straight out of the sensor.
Figure 2

Disconnect the mass airflow sensor electrical connector by pressing the release tab (red arrow) and pulling the connector straight out of the sensor.

Using a flathead screwdriver, loosen the mass airflow sensor duct clamp (red arrow).
Figure 3

Using a flathead screwdriver, loosen the mass airflow sensor duct clamp (red arrow).

Loosen the four T25 Torx fasteners from the intake air housing.
Figure 4

Loosen the four T25 Torx fasteners from the intake air housing.

Lift the intake air-housing lid up and detach the duct (red arrow) from the mass airflow sensor.
Figure 5

Lift the intake air-housing lid up and detach the duct (red arrow) from the mass airflow sensor.

Working at the mass airflow sensor, remove the two T30 Torx screws (red arrows).
Figure 6

Working at the mass airflow sensor, remove the two T30 Torx screws (red arrows).

Remove the sensor from the intake air housing lid (red arrow).
Figure 7

Remove the sensor from the intake air housing lid (red arrow). If stuck, use a small flathead screwdriver to gently lever it out of the lid.

Install a new mass airflow sensor into the air filter housing.
Figure 8

Install a new mass airflow sensor into the air filter housing. If the O-ring (red arrow) gives you a hard time going in, apply a small amount of dish soap to the O-ring. It will slide right in and the soap will not damage the O-ring. Check the vehicle for fault codes. See our tech article on reading and clearing fault codes. Then test drive the vehicle and confirm that the engine runs well.


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