What is a Map Sensor and Its Failing Symptoms

No, we’re not talking about your terrible navigation skills.

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Your car is full of electrical components that monitor and control various systems and functions. There are so many that it can be a real pain when one or more of them starts to act up. Complicating matters further is the fact that a failing sensor doesn't just send out incorrect information, it can cause ripple effects with other systems that rely on the readings.

One sensor that you may not have heard of is the MAP sensor or the manifold absolute pressure sensor. If that sounds completely foreign to you or makes you think of being lost on a country road while your spouse yells at you for not asking for directions, that's normal. The MAP sensor isn't exactly a household name.

The Drive's editors have spent enough time banging their heads against the wall trying to locate problem sensors to help you avoid the same fate. We’ll help you get started with diagnosing and fixing your MAP sensor, so grab your code reader and some patience and let's get started.

Your vehicle's MAP sensor actually has nothing to do with maps or navigation. It's an acronym for a component called the manifold absolute pressure sensor, which monitors airflow into the engine. This helps the vehicle's computer calculate the air density and adjust fuel delivery levels.

The MAP sensor can be located in one of a few different spots, depending on the vehicle, including under the dashboard, on the firewall, around the inner fender area, or near the intake manifold. Yours may be in a different location, so check your vehicle's service manual.

As the MAP sensor fails, it can cause various issues with the fuel system and vehicle performance. An inaccurate reading from the sensor will cause the computer to change the amount of fuel it sends, which can rob the engine of power or cause it to run poorly. If there's less fuel entering the engine, performance will obviously suffer, but it can also cause the engine to stall and cause a major safety issue.

As the sensor begins to fail, the vehicle's computer may also generate error codes. The codes correspond to specific problems with the sensor and can be read using an OBD2 (onboard diagnostics) device. The codes may include:

Although these codes are somewhat universal, some manufacturers’ codes are slightly different. It's important to research the codes and meanings for your specific make and model.

The sensor's operation involves physical and electrical components, so the cause of failure can involve a number of factors. If there is a leak or damage to the component's vacuum chamber, the sensor won't be able to get an accurate reading. Due to the sensor's location, it can also become dirty or obstructed by grime and debris from the engine bay or road.

The first thing you can do is to check for physical damage to the sensor and make sure that the wiring connections are solid. Next, you can use a voltmeter to check voltage and use an OBD-II scanner to read any error codes that have been generated.

The process of replacing a MAP sensor isn't all that complex and is made easier by the fact that the sensor is located in an easy-to-access location. You will need to be comfortable disconnecting the battery and using testing tools such as an OBD-2 scanner. You may also be able to just clean the sensor instead of replacing it. Refer to your vehicle's maintenance manual for more information.

Learn more about the world of MAP sensors with these related terms.

The combustion chamber is a part of a gasoline engine where fuel and air are ignited. The specific ratio of air and fuel is determined, in part, by the readings from the MAP sensor.

The engine control unit, or ECU, is an electronic device that monitors the performance of various components and systems. These smart devices gather information about the vehicle and make adjustments accordingly.

ECU can also stand for electronic control unit, which might also be called the electronic control module (ECM). Modern vehicles have dozens of ECUs and ECMs for the many different electrical and mechanical systems.

Onboard diagnostics, also known as OBD2, is a system through which a vehicle's ECUs generate alerts for various failures or issues. As the ECUs notice a problem, they generate codes that can be read using an OBD2 device. Codes correspond to specific problems that can help technicians or home mechanics diagnose and repair the vehicle.

Idle refers to the vehicle's engine speed when it's not in motion. When a vehicle is started cold, it generally roars to life and then settles into a steady engine rpm, which is its idle. The speed of idle may vary when the engine is cold and warming up.

Stalling refers to the stopping of an engine, either accidentally or through a failure or problem. People just learning to drive with a manual transmission frequently stall as they learn to shift gears, but stalls can also happen when there are problems with fuel delivery and other issues.

You’ve got questions, The Drive has answers!

A: This one's tough to answer, because the MAP sensor can be affected by so many different factors. If the vehicle is driven hard through rough, dirty terrain, it's reasonable to assume that the MAP sensor will be stressed harder and may be damaged.

A: It might be possible, but it's certainly not a great idea. If there's a problem with the air/fuel mixture, the engine can't perform at its best. Stalls, loss of power, and other unexpected changes in the vehicle's ability to run and drive normally can cause safety problems or may damage other parts of the vehicle's drivetrain.

A: Good news! MAP sensors don't break the bank when they need to be replaced. In general, you can expect to pay somewhere between $150 and $250 for the replacement including labor, most of which will go to pay for the part itself.

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