10 Symptoms of Bad MAP Sensor | How to Diagnose a MAP Sensor

A Manifold Pressure (MAP) sensor is one of the most critical components of your vehicle’s engine. The MAP sensor is a special engine sensor that detects the quantity of air pressure available in the intake manifold of a vehicle. Your vehicle’s air-fuel ratio might be affected if your MAP sensor ever fails. This article explains the bad MAP sensor causes, its symptoms, and how to fix it.

What is A MAP Sensor?

A manifold absolute pressure sensor, often known as a MAP sensor, is a kind of sensor that monitors the air pressure in the engine’s intake manifold.

The powertrain control module (PCM) uses the MAP sensor to control fuel injection rate, air-fuel mixture, and ignition timing to enhance engine efficiency, fuel efficiency, and emissions.

MAP Sensor

MAP sensors are most commonly used in engines with fuel injection. The engine’s air densities and mass air flow rate are used to compute the needed amount of fuel for optimal combustion and to impact the advance or retardation of spark timing.

As an alternative option, the intake airflow of a fuel-injected engine may be measured using a mass airflow sensor, also known as an MAF sensor.

Symptoms of bad MAP Sensor

A bad MAP sensor produces one or more of the below-given signs:

  1. Failed Emissions Test
  2. Check Engine Light
  3. Lean Air-Fuel Mixture
  4. Enhanced Emission Level
  5. Rich Air-Fuel Mixture
  6. Stalling
  7. Hard Starting Condition
  8. Rough Idle
  9. Bad Engine Performance
  10. Backfires

1) Check Engine Light

All the sensors in your car’s engine are continually monitored by the vehicle’s engine control unit while you drive. The check engine light will illuminate if these sensors’ readings are outside the prescribed range.

Check engine light

The check engine light will come on if your MAP sensor is sending incorrect information to the engine management unit.

DTC P0299, DTC P0133, DTC P0107, and DTC P0106 are examples of problems that often occur in automobiles equipped with turbochargers or superchargers.

2) Lean Air-Fuel Mixture

The air-fuel ratio that is too lean may have even more disastrous consequences:

  • Leaner combustion produces heat, which over time may harm or limit the lifespan of engine components due to excessive heat.
  • Air-fuel combinations that are less rich in oxygen create more toxic byproducts, including carbon monoxide (CO) and nitrous oxide (NOx) (NOx).
  • There is a higher probability of pre-detonation (also known as engine knock). It’s possible to lose a whole engine if a knock occurs when the vehicle is under a heavy load.

3) Rich Air-Fuel Mixture

A damaged or faulty MAP sensor may lead to a rich air-fuel mixture. The rich air-fuel mixture is very dangerous for the vehicle.

Read More: Symptoms and Causes of Bad Fuel Injector

4) Stalling

Engine stalling is one of the most common symptoms of a bad MAP sensor. When your sensor goes bad, your air-fuel mixture may be excessively rich or too low, which may create issues while the engine is idling.

When the engine is operating at idle, it is very sensitive; therefore, a poor air-fuel combination may initially be detected at idle.

Engine Stalling, symptoms of bad MAP sensor

Before replacing the sensor, make sure that the problem has been thoroughly identified.

5) Backfires


Backfires occur when your engine’s fuel is improperly ignited during combustion. The exhaust pipe may get clogged with unburned fuel if the combustion chamber is not properly heated. Exhaust pipes become quite hot, and this may cause the air-fuel combination to catch fire there.

The exhaust system will make a lot of noise, and your mufflers may even blow apart. If you’re unlucky, it might potentially catch fire in your automobile.

6) Hard Starting Condition

A malfunctioning MAP sensor might cause problems with the car’s start-up. The MAP sensor data is used by the car’s trip computer to measure the air pressure before the engine is started.

Hard Starting

At start-up, the engine is very sensitive to the appropriate air-fuel combination; thus, a bad reading may result in too little fuel being given to the engine, preventing the engine from starting.

7) Failed Emissions Test

Failed Emission Test due to a bad MAP sensor

If you reside in an area where passing an emissions test is required before you can register your car. In that case, a malfunctioning MAP sensor will most likely cause your automobile to fail an emission test.

8) Rough Idle

Rough Idle

When the engine is idling, severe vibrations or erratic changes in idle speed might be caused by an incorrect air-fuel ratio. This wrong air-fuel ratio is usually caused by a bad MAP sensor. 

9) Increased Emissions

Damage to the manifold absolute pressure sensor (MAP) might cause it to transmit an inaccurate signal to the powertrain control module (PCM), which may indicate an excessive or insufficient load on the engine.

Increased Emission Level, signs of a faulty MAP sensor

The air-fuel combination in your automobile must be just right in order for it to emit the correct amount of emissions. Even a little problem with the MAP sensor might cause the fuel mixture to become unstable, resulting in a disturbance of emissions.

10) Bad Engine Performance

The engine’s performance will suffer as a result of an incorrect fuel mixture. A lean mixture often diminishes engine performance, but it may also be brought on by a mixture that is overly rich. Misfires produced by a malfunctioning MAP sensor may also cause poor engine performance.

Poor Acceleration

MAP Sensor Replacement Cost

If you’ve found that your MAP sensor has failed, don’t worry; replacing the sensor is inexpensive and straightforward. In reality, most individuals could easily do this in their own garage and save significant money.

According to the automobile model and labor expenses, the cost of a new MAP sensor varies widely. The average replacement cost of a bad MAP sensor is from $40 to $190. In this cost, the labor cost is between $20 and $80, while the sensor itself cost is between $20 and $110.

Replacement of the MAP sensor on most automobile models is usually simple and may be done at home. If you have a little automobile expertise, you can save money by doing the repairs yourself.

MAP Sensor Location

Typically, the MAP sensor is located in the intake manifold. In the case of a forced-induction engine, the sensor is situated in the intake path just prior to the turbo. The MAP sensor features a calibrated sealed chamber, which is tailored for each engine to deliver the appropriate vacuum or regulated pressure levels.

MAP Sensor Location

The exact location of the MAP sensor may differ based on the vehicle design, so it is recommended to consult your car’s service manual to determine the specific placement.

How to Diagnose a Bad MAP Sensor

Follow the below-given steps to find a fault in your MAP sensor:

  1. First of all, park your vehicle on a flat surface.
  2. Find the MAP sensor. The location of the MAP sensors varies according to the vehicle module and engine design. Therefore, it is recommended to check the vehicle’s manual to quickly find the sensor.
  3. Properly inspect the vacuum hoses that link the engine to the MAP sensor. Vacuum hoses shouldn’t be damaged. If they are damaged, repair or replace them as soon as possible.
  4. Inspect the electrical wiring and connections to the sensor.
  5. If your sensor is dirty, then clean it properly by using an electronic.
  6. Properly inspect the MAP sensor for damage. If it is damaged, replace it immediately to ensure the efficient working of your engine.

FAQ Section

Can I drive with a bad MAP sensor?

It is not recommended to drive with a bad MAP sensor. When the MAP sensor malfunctions, your engine consumes more fuel than necessary, which can damage the engine and potentially affect the exhaust system. Within the exhaust system, the catalytic converter is particularly susceptible to harm caused by a problematic MAP sensor.

What is the function of a MAP Sensor?

The main purpose of a MAP sensor is to calculate the intake manifold pressure and deliver this data to the engine’s electronic control unit (ECM). The ECM data utilizes this information to measure the fuel injector rate and air density.

Does cleaning the MAP sensor work?

MAP sensors don’t have moving components and don’t normally wear out, although cleaning the MAP sensor may be necessary if it is polluted by carbon or other engine deposits. A possible cause of voltage slowness when pressure changes might be contamination.

Can a MAP sensor cause misfire?

When a MAP sensor provides an inaccurately high-pressure reading, the engine control unit (ECU) will instruct the engine to use more fuel. This leads to a rich air-fuel mixture, which may contaminate the spark plugs and cause a cylinder to fail to ignite. An engine with misfiring cylinders will vibrate, and this movement can be felt inside the vehicle’s cabin.

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