2AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEMES–109
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DESCRIPTION
The Intake Air Temperature (IAT) sensor, mounted on the Mass Air Flow (MAF) meter, monitors the IAT.
The IAT sensor has a built-in thermistor with a resistance that varies according to the temperature of the
intake air. When the IAT is low, the resistance of the thermistor increases. When the temperature is high,
the resistance drops. These variations in resistance are transmitted to the ECM as voltage changes (See
Fig. 1).
The IAT sensor is powered by a 5 V supply from the THA terminal of the ECM, via resistor R.
Resistor R and the IAT sensor are connected in series. When the resistance value of the IAT sensor
changes, according to changes in the IAT, the voltage at terminal THA also varies. Based on this signal,
the ECM increases the fuel injection volume when the engine is cold to improve driveability.
MONITOR DESCRIPTION
The ECM performs OBD II monitoring based on the values from the intake air temperature sensor. If there
is no change of the sensor value within the normal range, the ECM will not be able to perform OBD II
monitoring or will misdiagnose that there is a malfunction in the sensor. The ECM detects the stuck intake
air temperature sensor value by performing monitoring after the ignition switch is turned OFF or the
engine is started (short soak or long soak).
DTC P0111Intake Air Temperature Sensor Gradient Too
High
DTC No. DTC Detection Condition Trouble Area
P0111When either condition below is met:
1. The intake air temperature rise is large, from the
previous trip warm-up to the following trip (2 trip
detection logic).
2. When the change in the intake air temperature after
engine start is less than the threshold value.Mass air flow meter assembly
A067628E18
2AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEMES–111
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(b) Turn the ignition switch ON.
(c) Turn the tester ON.
(d) Enter the following menus: DIAGNOSIS / ENHANCED
OBD II / DTC INFO / CURRENT CODES.
(e) Read DTCs.
Result
HINT:
If any DTCs other than P0111 are output, troubleshoot
those DTCs first.
B
A
Display (DTC Output) Proceed to
P0111 and other DTCs A
P0111 B
REPLACE MASS AIR FLOW METER
GO TO DTC CHART
