MAP/MAF SENSORS

Q: What does a MAF sensor do?

Based on the air mass information, the engine control unit (ECU) is able to balance and deliver the correct fuel quantity to the engine. In diesel engines, the MAF sensor serves mainly to control the exhaust gas recirculation (EGR). The majority of MAF sensors come in two variations: hot-wire technology and hot-film technology. These MAF sensors have no moving parts and use electrical current to measure air mass.

Q: Where is the MAF sensor located?

The MAF sensor is located between the intake manifold and the air filter.

Q: What are the symptoms of a bad MAF sensor?

MAF sensors can degrade in quality over time as well as becoming prone to failure if they get too dirty, which can be caused by exposure to dust, water and oil. Symptoms of a faulty MAF sensor to look out for include the ‘check engine light’ being turned on, reduced fuel economy, difficulty starting the engine, lean idling, black exhaust smoke, unstable engine running, engine power loss and engine misfiring.

Q: How is a MAF sensor tested?

To perform an initial, quick check while driving, full throttle should be executed in gear three or four. This will provide a maximum pressure boost. During this drive the parameter list in the scan tool should be checked by a second person. The calculated and measured values should then be compared, and both should correspond. If no values are available in the scan tool, the output voltage of the MAF needs to reach approximately 4V.

Q: What is the normal MAF sensor reading?

A normal MAF output voltage is between 0.2V and 4.8V.

Q: What does a MAP sensor do?

Standing for ‘manifold absolute pressure’, a MAP sensor supplies instant manifold pressure information to the ECU. The data is needed to calculate air density and determine the engine's air mass flow rate. This, in turn, determines the fuel required for optimum combustion.

Q: Where is a MAP sensor located?

The MAP sensor is usually located in the intake manifold or pressure hose.

Q: What are the symptoms of a bad MAP sensor?

Just like MAF sensors, MAP sensors can also degrade in quality over time as well as becoming prone to failure if they get too dirty. Symptoms of a faulty MAP sensor to look out for include the ‘check engine light’ being turned on, reduced fuel economy, difficulty starting the engine, lean idling, black exhaust smoke, unstable engine running, engine power loss and engine misfiring.

Q: How is a MAP sensor tested?

This can be performed with a vacuum pump. With the MAP sensor kept electrically connected, the pump should then be attached to the measuring chamber of the sensor. The output voltage can then be measured. A scan tool can also be used to observe a signal. This signal, moreover, must modify according to pressure applied.

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MAP and MAF sensors have become an integral part of the engine management system. Their task is to send information to the vehicle’s Engine Control Unit (ECU), enabling it to control the air-fuel mixture needed by the engine to operate efficiently. NTK MAP and MAF sensors undergo rigorous tests to ensure they meet or even exceed the highest standards.

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MAP/MAF Sensor Types

The majority of MAF sensors come in two variations: hot-wire technology and hot-film technology. These MAF sensors have no moving parts and use electrical current to measure air mass.

MAP sensors can be classified in two groups: manifold pressure type and boost pressure type. They provide immediate data on the manifold/boost pressure to the ECU, measuring air pressure to make calculations for fuel, and ignition calibration, which is vital to maintain engine efficiency.

MAP/MAF Sensor Function Principles

Situated between the intake manifold and the air filter, the MAF sensor is a vital part of the engine management system and determines the amount of air flowing into the intake system of diesel and petrol combustion engines. Based on the air mass information, the engine control unit is able to balance and deliver the correct fuel quantity to the engine. In diesel engines, the MAF sensor serves mainly to control the exhaust gas recirculation (EGR).

The MAP sensor measures the air pressure by the deformation of a membrane with integrated resistors. The pressure varies depending on the throttle position, engine speed and turbo operation. The Boost Pressure Sensor, in turn, is used in turbocharged engines and located between the turbocharger and intake manifold.