MAP Sensor Working Principle and Replacement Cost


The engine control unit is connected to numerous sensors throughout a vehicle. Based on the information these sensors end up detecting, the engine control unit will initiate certain functions to ensure that the engine performs at its best.

Basic Function

The manifold absolute pressure sensor is a component of the intake manifold. This sensor measures how much air pressure currently exists inside the manifold. It then reports this data to the engine control unit where the calculation can be confirmed. Other information the MAP sensor will consider is the air temperature and the number of rotations that take place per minute inside of the engine. From there, the engine control unit will use this information to regulate how much air and fuel get sent into the internal combustion chamber.

Basically, the MAP sensor is checking on the engine load. If there is a heavy load, then the engine must work harder to sustain it. Meanwhile, the vacuum pressure in the intake manifold will decrease because the throttles will be open fully. Once this happens, more air will get pulled into the engine from the environment than normal. Since the internal combustion chamber is supposed to have a balance of air and fuel, the fuel injectors will place more fuel in the chamber. Whenever the MAP sensor tells the engine control unit that a heavy load exists, the fuel mixture will become denser because more power is needed for the engine to sustain this load.

The Principle

A vacuum hose connects the MAP sensor to the intake manifold. Whenever the engine gets turned on, a vacuum effect forms within the intake manifold. This is a result of the pumping movements of the pistons and the restriction being generated from the throttle plates. If the throttle plates are opened completely while you have a running engine, the vacuum pressure in the intake manifold will not be there. This will cause the engine control unit to provide more fuel to the internal combustion chamber. But if the intake manifold has more vacuum pressure, the MAP sensor will have a weaker signal. This will tell the engine control unit to have less gasoline enter the chamber.

Whatever the vacuum pressure measurement is, this information gets sent as an electrical signal to the engine control unit. Remember this unit is the main computer of the vehicle which performs certain functions based on absolute pressure. This pressure is equal to the atmospheric pressure and the manifold pressure. Using information pertaining to the density and speed of the atmospheric pressure, the engine control unit will calculate the mixture of fuel in the chamber. This calculation needs to be correct in order for the engine to perform properly. If the air and fuel mixture is incorrectly calculated, then the engine will not be able to handle the load it is being given.

Read also: 4 Types Spark Plugs: Iridium, Copper, Regular Platinum and Double Platinum

Replacement Cost

Despite how important the MAP sensor is to a car, they are not that expensive to replace at all. In fact, most of the money that you will spend on replacing the component will go toward the labor costs. The total replacement cost of a MAP sensor will depend on the make and model of the vehicle. The average cost will be around $120 to $210 total. Most of this expense comes from the cost of the part itself. This is about $90 to $140 in most cases. The labor costs will be anywhere from $30 to $70. You can also expect there to be added fees and taxes on top of these prices. Overall, you shouldn’t end up spending more than a couple of hundred dollars.


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