Freelander System Description and Operation
ENGINE MANAGEMENT SYSTEM - SIEMENS
18-4-20 DESCRIPTION AND OPERATION
MAF Sensor
The MAF sensor provides a signal which the ECM uses for engine load calculations.
The MAF sensor is a hot film type, and is located in the intake system between the air filter housing and the throttle
body.
A closed-loop control circuit in the MAF sensor maintains a thick film resistor at a constant 200
°
C (392
°
F) above
ambient temperature. The current required to maintain the temperature of the thick film resistor, against the cooling
effect of the air flowing through the sensor, provides a precise, non-linear, measure of the air mass entering the
engine.
The MAF sensor receives a battery voltage power supply and generates an output signal to the ECM, between 0 and
5 volts, which is proportional to the air mass drawn into the engine.
In the event of a MAF sensor signal failure, the following symptoms may be apparent:
l
During driving engine speed may dip before recovering.
l
Difficult starting.
l
Engine stalls after starting.
l
Delayed throttle response.
l
Reduced engine performance.