There are many reasons why your manifold absolute pressure (MAP) sensor would trigger your "check engine" light. But if your diagnosis reveals a code that indicates irregular intake manifold pressure or a vacuum leak, then your sensor is working properly. But you can also get a "check engine" light when your manifold sensor isn't working. Just like other intake and fuel delivery components, a poorly or non-functioning sensor on your intake manifold will result in suboptimal fuel efficiency and power output. Without it checking the pressure, your engine control module has no way of knowing the density of the air inside the intake so it cannot complement it with the appropriate levels of fuel to mix with it. Aside from poor performance and gas mileage, a faulty MAP sensor may also prevent you from accelerating quickly or using your cruise control. Plus, you will almost certainly idle very roughly and stall frequently due to a lack of combustible fuel.
Many people will confuse their MAP and their MAF (mass air flow) sensors, since they sound very similar and perform very similar functions. They are, however, different parts. Your MAP sensor is located right at the intake manifold and measures the absolute pressure of the air stored inside. The MAF sensor is located much further forward, in the intake hose behind the air box, and it measures the volume of the air entering the intake manifold. Both sensors transmit their signals to the onboard computer for processing, and it returns the appropriate levels of fuel for optimal combustion. Another function of the MAP sensor is that it also checks the EGR valve's functionality. This is crucial in passing your next emissions test.
Since your manifold absolute pressure sensor is located right at the intake manifold, it is typically easy to find and replace. There will be a wire harness connected to it, as well as a couple of vacuum lines. To replace it, you simply have to disconnect these lines and wires, unbolt it from the manifold, and put in a new one. Be advised, you should disconnect your battery first to prevent accidental electrocution. When it gets reconnected, your "check engine" light should go off.
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