4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS
6E–47
Mass Air Flow (MAF) Sensor & Intake Air
Temperature (IAT) Sensor
The mass air flow (MAF) sensor is part of the intake air
system.
It is fitted between the air cleaner and turbocharger and
measure the mass air flowing into the engine.
The mass air flow (MAF) sensor uses a hot film element
to determine the amount of air flowing into the engine.
The mass air flow (MAF) sensor assembly consist of a
mass air flow (MAF) sensor element and an intake air
temperature sensor that are both exposed to the air flow
to be measured.
The mass air flow (MAF) sensor element measures the
partial air mass through a measurement duct on the
sensor housing.
Using calibration, there is an extrapolation to the entire
mass air flow to the engine.
The IAT sensor is a thermistor. A temperature changes
the resistance value. And it changes voltage. In other
words it measures a temperature value. Low air
temperature produces a high resistance.
The ECM supplies 5 volts signal to the IAT sensor
through resisters in the ECM and measures the voltage.
The signal voltage will be high when the air temperature
is cold, and it will be low when the air temperature is hot.
Pedal/Throttle Position Sensor (TPS)
-30 -20 -10
0
10
20
30
40
50
60
70
80
90
100 110 120 130
Characteristic of IAT Sensor
Temperature (
o
C)
Resistance ( )
(1) Throttle Position Sensor (TPS)
(2) Idle Switch
1
2
+5V
Output
Ground
+5V
Ground