Mass Air Flow (MAF) Sensor/Intake Air Temperature (IAT) Sensor

Courtesy of VOLVO CARS CORPORATION

Overview 

The mass air flow (MAF) sensor is a combined sensor and contains two sensors in the same component:

• mass air flow (MAF) sensor
• intake air temperature (IAT) sensor.

The mass air flow sensor is located by the air filter housing.

Mass air flow sensor (MAF) 

The mass air flow (MAF) sensor gauges the air mass sucked into the engine. It continuously transmits signals to the engine control module (ECM) about the mass of the intake air. This data is used by the engine control module (ECM) to calculate:

• the injection period
• the fuel pressure
• the ignition timing
• the engine load.

The transmission control module (TCM) also uses this data for its gear shift calculations. This data is transmitted to the transmission control module (TCM) from the engine control module (ECM) via the high speed side of the Controller area network (CAN).

The mass air flow (MAF) sensor is a hot wire type. Unlike other hot wire types, the mass air flow sensor in the Denso system uses a hot wire which has a ceramic casing. This eliminates the need for a clean burn function.

The mass air flow (MAF) sensor is supplied with battery voltage by the system relay and is grounded in the engine control module (ECM). The signal from the sensor is analog and varies between approximately between 0.5 - 4.5 V. Low air flow (low mass) results in low voltage, high air flow (high mass) gives high voltage.

The mass air flow (MAF) sensor can be diagnosed by the engine control module (ECM) and the sensor signal can be read off.

Intake air temperature (IAT) sensor 

The temperature sensor checks the temperature of the intake air in the intake manifold. This data is used by the engine control module (ECM) to calculate injection period. The control module also controls certain diagnostic functions using the signal from the temperature sensor.

The sensor, which is an NTC resistor, is grounded in the control module and supplied with power (signal) from the control module.

The resistance in the sensor changes according to the intake air temperature. This provides the control module with a signal of between 0.5 - 5 V. The lower the temperature the higher the voltage (high resistance). A high temperature results in low voltage (low resistance).

The temperature sensor can be diagnosed by the engine control module (ECM) and the sensor signal can be read off.