7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 451
IAT Sensor (Intake Air Temperature)
Figure 456 Function diagram for the IAT sensor
The function diagram for the IAT sensor includes the
following:
• IAT sens or
• Electronic Control Module (ECM)
• Fuel injector
• ENGIN E lamp (am ber)
Function
The Intake Air Temperature (IAT) sensor is a
thermistor sensor that is chassis m ounted on the
air filter housing. The ECM supplies a 5 V reference
signal which the IAT sensor uses to produce an analog
voltage that indicates the intake air temperature.
The IAT sensor changes resistance when exposed
to different temperatures. As air tem perature
decreases, the resistance of the thermistor increases.
This causes the signal v oltage to increase. As
air temperature increases, the resistance of the
thermistor decreases. This causes the signal voltage
to decrease.
The IAT sensor provides a feedback signal to the ECM
indicating intake air temperature. The ECM monitors
the IAT signal to control the timing and fuel rate for
cold starting. The continuous monitoring by the IAT
sensor limits smoke emissions.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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