Air Flow Meter/Sensor: Description and Operation

MASS AIR FLOW SENSOR

The Mass Air Flow (MAF) sensor measures the engine intake air mass and supplies the ECM with continuous signals, which the module uses to compute the following:

^ Injection period
^ Ignition timing
^ Turbo Charger (TC) boost pressure (only turbo)
^ Post-running of the engine cooling fan

The TCM also uses the information to perform gear-change computations

The MAF sensor consists of a plastic housing containing a connector, electronic circuitry and an aluminum heat sink. The measuring element consists of a hot film, consisting of four resistances, which is cooled by the intake air flow.

The MAF sensor, which receives a 12 Volt supply from the main relay, has separate power and signal grounds. The sensor signal varies from 0 Volts to 5 Volts, depending on the air mass, and increases with the flow.

Since the working temperature is relatively high (179°C / 338°F), and the flow and temperature sensitive resistances are mounted on the side of the hot film, a burn-off function is not required.

The ECM will adopt a substitute value if the MAF sensor signal is lost or becomes faulty.

The sensor is mounted on the Air Cleaner (ACL) cover.