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Mass Air Flow Sensor Replacement
 
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Pelican Technical Article:

Mass Air Flow Sensor Replacement

Jared Fenton

Time:

1 hour1 hr

Tab:

$120

Talent:

**

Tools:

Flathead screwdriver

Applicable Models:

Volvo C30 T5 (2008-13)
Volvo C30 T5 R-Design (2008-13)

Parts Required:

Mass Air Flow Sensor

Hot Tip:

Sometimes dirty MAFs can be cleaned

Performance Gain:

Smoother running engine, better MPG

Complementary Modification:

Clean throttle body

The mass air flow sensor (MAF) is located inside the intake system and is used to measure the amount and temperature of air that is entering the engine at any given time. The MAF senses the total amount of air passing the sensor and allows the fuel injection system to adjust the fuel mixture to compensate for cold weather and/or high altitude conditions.

The first indicator that you may have a problem with the MAF is the presence of a check engine light (CEL) on your dashboard. The CEL can be caused by a wide variety of problems with the engine: you need to read the diagnostic trouble codes (DTC) from the computer to get a starting clue as to what the problem is. Sometimes, there is no change in how the engine is running. Other times, you might experience a loss in power, sluggish running and a decrease in gas mileage as a result.

The computer will know if something is wrong with the MAF because it will compare the values being output by the sensor to "expected" values that it should be receiving. This common-sense check by the computer helps to diagnose problems with every component in the system. If the MAF becomes dirty and is falsely indicating to the engine that the car is receiving very little air while at full throttle, then the computer will most likely trigger a DTC and light up the CEL on your dash.

To read the DTC, you'll need to access the on board diagnostic (OBD) connector under the dashboard. Through this connector, a computer is able to retrieve the codes using a diagnostic software package. Products such as VADIS are invaluable for this and other diagnostic tasks. However, for those of you on a budget, many auto parts stores have a generic hand held scanner that can retrieve codes. Usually for free as well. In this case, simply write down the DTC and look it up online.

Vacuum leaks and other air leaks in the system can also cause MAF sensor errors. If you have a crack or leak in your air intake downstream of the sensor, then the MAF will be sensing less air than the engine is actually receiving. Always check the intake system for leaks. I've often seen poor running engines that ran smooth once a hose clamp was tightened.

Cleaning the MAF involves removing the actual sensor from the mounting tube. To do this, you'll need a tamper-proof T25 Torx driver. Once free, use a can of MAF sensor cleaner (available at any auto parts store) to spray off the hooked end of the sensor. Follow the directions on the side of the can for best results.

After you have replaced or cleaned the sensor and cleared the DTC with a scanner, you need to go drive the car and see if the code returns (usually around 10-20 miles). If the same error code appears, then the problem probably lies elsewhere. Most of the time when you have an error code indicating a problem with the mass air flow sensor, it is usually solved by the installation of a new sensor. However, the computer can become confused sometimes and give misleading error messages. Wire harness issues, DME problems, and vacuum leaks may all give false MAF error codes. At this point, it's best to dive into the factory manuals and start going through the laborious test procedures contained in there.

Shown here is the MAF sensor housing mounted in the intake near the airbox (green arrow).
Figure 1

Shown here is the MAF sensor housing mounted in the intake near the airbox (green arrow). You'll need to remove the turbo crossover pipe to access the MAF. See our article on Spark Plug and Coil Pack Replacement for more information.

The next step is to remove the two T25 Torx screws holing the MAF to the airbox.
Figure 2

The next step is to remove the two T25 Torx screws holing the MAF to the airbox. This picture shows the upper screw (green arrow). The lower screw is directly opposite of the top one and impossible to get aPicture of. Once the screws are removed, pull the MAF out.

Flip the MAF over to access the electrical connection.
Figure 3

Flip the MAF over to access the electrical connection. Pull up on the locking tab (green arrow) and pull the connector off the MAF.

Pull off the rubber sealing grommet (green arrow) and place it back into the airbox.
Figure 4

Pull off the rubber sealing grommet (green arrow) and place it back into the airbox.

Shown here is the business end of the MAF sensor.
Figure 5

Shown here is the business end of the MAF sensor. You can try using some MAF cleaner spray to get things working again. Installation is the reverse of removal.

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