Function

Function

The sensor measures atmospheric pressure. Depending on the information received, the engine management control unit:

• determines the density of the air
• inhibits recirculation if driving at high altitude

NOTE Air pressure decreases as altitude increases.

Description

The sensor is the piezoelectric type and consists of stress meters.
The sensor supplies a voltage proportional to the atmospheric pressure.

Location

The atmospheric pressure sensor is incorporated in the injection control unit.

WARNING The atmospheric pressure sensor cannot be separated from the injection control unit.

EXHAUST GAS RECIRCULATION SYSTEM

FLOW METER (AIR FLOW METER)

Function

The air flow meter measures the mass of air drawn in by the engine. According to the information received, the injection control unit:

• determines the recirculation rate for the exhaust gases
• limits the formation of black fumes during transition stages (acceleration, deceleration) by correcting the fuel flow rate.

Description

The flow meter consists of the following elements:

• metal plate (hot film)
• air temperature sensor.

The metal plate, which is very thin, makes it possible to determine the mass of air entering the air circuit. It consists of a heating resistance and a measuring resistance (NTC).

The injection control unit supplies the heating resistance so that the metal plate is kept at a constant temperature. The air passes into the meter and cools the metal plate, altering the measuring resistance. The control unit associates the resistance value with an air flow rate.

WARNING Do not touch the metal plate (hot film). It is forbidden to use an air jet.