What does a MAP Sensor do for your vehicle?

There are a myriad of sensors underneath your hood that quietly do their jobs day in and day out without making a fuss.  They may not be as visible as a mass air flow sensor or as talked about as a camshaft sensor, but they all have important jobs. With the rise of fuel injection in the 1980s the Manifold Absolute Pressure (MAP) sensor became an important asset to engine management. But what does a MAP sensor do for your vehicle?

Where Is The MAP Sensor Located?

The MAP sensor is typically located in the air cleaner, fender wall, firewall, intake manifold or under the dash. It needs to be connected to the intake manifold in some way, either by being placed directly on it or by a hose. It is important that the MAP sensor be able to read the air pressure inside the intake manifold precisely.

What Does A MAP Sensor Do?

The MAP sensor converts engine vacuum/manifold pressure to an electrical signal so the computer knows how much load the engine is under. This data is the basis for fuel delivery and timing control. An engine is essentially an air pump, but in order to accurately meter out the right amount of fuel it is important to know how much air is being pumped. The MAP sensor helps the computer understand the air density and therefore the engine’s mass air flow. Speed density fuel injection systems rely on the MAP sensor to help make an educated guess at engine air flow. Alternately mass air flow fuel injection systems use a dedicated mass air flow meter to accurately measure engine air flow. Both systems have their preferred applications.

Will A Malfunctioning MAP Sensor Illuminate The Check Engine Light Or Affect Vehicle Operation?

Yes, a failing sensor can illuminate the malfunction indicator lamp (MIL), and may cause the engine to have a rich or lean fuel mixture condition. This could affect fuel economy and also possibly damage the catalytic converters. Use an OBD II scanner to read the trouble codes if the check engine light is on. OBD trouble codes P0105,  P0106, P0107, P0108, and P0109 may also be stored in the computer memory.

What Are The Common Causes of MAP Sensor Failure?

Typically a MAP sensor relies on a perfectly sealed vacuum chamber inside attached to a diaphragm that moves with variations in intake manifold pressure. Typically these sensors fail due to moisture entering the sensor when the engine is off and due to normal wear of the sensor element. If the MAP sensor relies on separate hose make sure to check the hose for cracks or leaks that may cause a vacuum leak causing an incorrect reading. Usually due to the sensitive internal parts a MAP sensor cannot be repaired, only replaced.

How To Determine If A MAP Sensor Is Malfunctioning?

The Diagnostic Monitor tests for voltages outside of the normal range. The PCM also compares actual MAP output to calculated values to determine sensor performance deterioration. The calculated values are based on TP and various engine load factors.

How To Replace A MAP Sensor

While the exact procedure for MAP sensor replacement will vary from vehicle to vehicle, the following video gives a look at a typical MAP sensor replacement procedure:

For the exact procedure to replace your MAP sensor, refer to the specific repair and maintenance manual for your vehicle. You may also opt to clean your MAP sensor before opting for outright replacement.

Check out all the relays, sensors and switches available on NAPAOnline or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on your vehicle’s MAP sensor, chat with a knowledgeable expert at your local NAPA Auto Parts store.

Photo courtesy of Wikimedia Commons.