In modern vehicles, a computer and a series of sensors control the engine’s fuel consumption and other operations. While you may never have to work on any of these sensors yourself, one in particular is essential to a smoothly running engine — the MAP (manifold absolute pressure) sensor. What is a MAP sensor, and what does it do? When your engine is running funny, it could indicate a failure of this sensor, so here’s a look at what exactly it is that the MAP sensor does.
In fuel-injected automotive engines, a manifold absolute pressure (MAP) sensor is used to continuously monitor the amount of air flowing into the engine, so the computer can calculate air density, adjust the amount of fuel to spray into the combustion chamber and adjust the ignition timing. In some vehicles, a mass air flow (MAF) sensor is used. While the two are interchangeable, a MAF sensor measures flow rather than density.
A failed MAP sensor can cause your vehicle to have a few performance problems. If the sensor is in error, reading too high, it can cause the fuel management system to use more fuel than is needed and decrease fuel economy. Conversely, if the MAP sensor reads too low, the onboard computer will trim back the amount of fuel it thinks is needed and starve the engine, causing it to run erratically and decrease power. In either case, if the sensor isn’t reading properly, it will cause your vehicle to fail emissions testing. Plugging in a diagnostic code reader you may find trouble codes P0068, P0069, P1106, or P1107.
Reasons for a MAP sensor failure can be caused by a few factors. The sensor itself relies on both electronic and mechanical components to function. A vacuum chamber inside the sensor is what allows the the sensor to read changes in the manifold pressure. Over time a leak can develop in the vacuum chamber, making the sensor unable to read correctly. Due to the location of the sensor in the harsh engine compartment environment, years of extreme temperature fluctuations and vibration can also wreak havoc on the internal circuitry. Another failure point can be dirt or other contamination physically preventing the sensor from accessing the intake manifold air flow.
Difficulty in replacing a bad MAP sensor varies by vehicle. Typically, it’s mounted to the outside of the intake manifold or throttle body using a set of bolts or screws. Unplug the sensor wire and then undo the screws and carefully remove the bad sensor. To install your new one, simply reinstall the screws, plug the wire back in and you’re ready to go. Depending on the vehicle and if a trouble code was set, a diagnostic tool may be required to reset the check engine light.
Many people hear that they have a bad sensor and wonder: What is a MAP sensor? While its job may be a simple one, it’s essential to getting good fuel economy and performance out of your vehicle’s engine for years. If you suspect a MAP sensor failure, your local NAPA AutoCare center has the expertise to handle the problem and get you back on the road.
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Erich Reichert has been an editor and on-air personality in the radio control car hobby for 12 years. A certified car nut since birth, he has written for internationally published titles such as RC Car Action, RC Driver and Xtreme RC Cars, as well as Stuff Magazine, Road and Track and Super Street. He's covered everything from product reviews and tech articles to high-profile lifestyle pieces and celebrity interviews. Erich found his passion for writing after a successful career as an art director, working with brands such as Pepsico, NASCAR, MTV, Nintendo, WWE, Cannondale Bicycles and HBO. He's also a father, an avid hockey fan and an FIA race license holder who enjoys hiking, playing drums and movies.