How to Check if Your MAP Sensor is Bad

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Balance is vital in engine performance. The right amount of air, the right amount of fuel, proper ignition timing—all of these affect how the engine operates. There is a complex system in place ensuring everything is clicking on all cylinders; and in this network of parts, usually located around the upper engine bay area, is an intuitive contraption called the MAP sensor.

This sensor aids the Powertrain Control Module (PCM) in keeping the engine running smoothly, which should be top priority, especially during long drives under extreme weather. For instance, summer–a season notorious for breaking down engines due to its punishing temperatures.

Though a small component, the MAP sensor is crucial in ensuring optimal engine performance.

What’s a MAP Sensor?

The manifold absolute pressure (MAP) sensor processes signals based on the pressure in the intake manifold and transmits them to your car’s computer, so it can calculate for ideal engine load, spark advance, and fuel injection pulse. Inaccuracies in any of these can result in diminished performance and engine damage.

In other words, in order to secure the best combustion possible, the MAP sensor should operate with sharp precision. If it fails and starts feeding the PCM with erroneous signals, you can expect your air-fuel ratio to become either too lean (less fuel) or too rich (more fuel).

A MAP sensor fails when:

Signs of a Bad MAP Sensor

So what happens when your MAP sensor has gone kaput? Here are the most common consequences:

A defective MAP sensor can cause you to fail your emissions test.

It helps to be aware of the signs of a bad MAP sensor so you can act fast to remedy the problem. Or, better be proactive by inspecting your MAP sensor during routine maintenance checkups. You can use a scan tool for this (your MAP sensor reading at idle should have a reference voltage close to five volts) and administer a bench test using a hand vacuum pump and a voltmeter.

Make it a habit to check your MAP sensor from time to time to maintain a sense of balance in your engine’s operation and ensure optimum performance for your car.

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In the Garage with is an online blog dedicated to bringing DIYers and devoted car enthusiasts up to date with topical automotive news and lifestyle content. Our writers live and breathe automotive, taking the guess work out of car repairs with how-to content that helps owners get back on the road and keep driving.

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