Dtc22 - Iat Sensor System Fault - Isuzu 4HL1 Workshop Manual

DTC22 - IAT Sensor System Fault

Circuit Description
The IAT (intake air temperature) sensor consists of
thermistor and alters the resistance in response to
temperature change. Higher intake air temperature
provides smaller resistance while lower temperature
provides larger resistance. The ECM supplies 5 V to
the IAT sensor via pull-up resistance and calculates the
intake air temperature from the change in voltage and
uses it in fuel injection control and other control tasks.
The voltage is decreased when the resistance is small
(the temperature is high) while increased when the
resistance is large (the temperature is low).
DTC22 will be set when the signal voltage is
excessively high or low.
Major Faulty Event
• Poor driveability
• Generation of white smoke
Conditions for Setting the DTC
The IAT sensor output voltage deviates from the range
between 0.1 V and 4.9 V for at least 3 seconds.
Action Taken When the DTC Sets
• After the DTC is set, the ECM will illuminate the
CHECK ENGINE lamp (MIL).
• The ECM controls the powertrain using the set
intake air temperature (–10°C).
ECM
(Engine
Control
Module)
91 83
IAT
Sensor
Conditions for Clearing MIL/DTC
When the system fails and the DTC is stored to the
ECM, even repairing the faulty portion will not clear the
DTC from the memory. To clear the DTC, conduct the
following steps.
1. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
2. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
3. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
4. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
5. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
6. After the above operations are properly completed,
the CHECK ENGINE lamp (MIL) illuminates for 3
seconds to report the memory is cleared.
7. Turn off the starter switch. Wait for 5 seconds and
turn on the starter switch again.
When Tech 2 has been connected to the vehicle, the
DTC can be cleared through the memory clear
operation with Tech 2.
Engine Control System 1A-103
LNW21AMF007701-X