Toyota Sienna Service Manual: Intake Air Temperature Sensor Gradient Too High
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 becomes low, the resistance of the thermistor increases. When the temperature becomes 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 in the sensor value, 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 ignition is started (short soak or long soak).
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
WIRING DIAGRAM
Refer to DTC P0110 (See page ES-126).
INSPECTION PROCEDURE
1 CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0111)
(a) Connect the intelligent tester to the DLC3.
(b) Turn the ignition switch to the ON position.
(c) Turn the tester on.
(d) Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
(e) Read the DTCs.
Result
HINT: If any DTCs other than P0111 are output, troubleshoot those DTCs first.
GO TO DTC CHART (See page ES-56)
Intake Air Temperature Circuit
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 accord ...
Engine Coolant Temperature Circuit
DESCRIPTION
A thermistor is built into the Engine Coolant Temperature (ECT) sensor, of
which the resistance value
varies according to the ECT.
The structure of the sensor and its connection ...
Other materials:
Removal
1. DISCONNECT BATTERY NEGATIVE TERMINAL
2. REMOVE FRONT DOOR SCUFF PLATE LH
HINT:
(See page IP-6)
3. REMOVE FRONT DOOR SCUFF PLATE RH
HINT:
(See page IP-6)
4. REMOVE COWL SIDE TRIM BOARD LH
HINT:
(See page IP-6)
5. REMOVE COWL SIDE TRIM BOARD RH
HINT:
(See page IP-6)
6. REMOVE INSTRUMEN ...
Reassembly
1. INSTALL LOWER RADIATOR GRILLE
Engage the 16 claws to install the lower radiator
grille to the front bumper cover.
2. INSTALL FRONT BUMPER HOLE COVER LH (w/o
Fog Light)
Engage the 2 pins to install the front bumper hole
cover LH to the front bumper cover.
3. INSTALL FRON ...
Releasing and stowing the seat belt (for the third center seat)
To release plate “B”, press the
release button on buckle “B”.
To release plate “A”, insert the
key or plate “B” into
the hole on buckle “A”.
Retract the belt slowly when
releasing and stowing the seat
belt.
Insert the seat belt plates into
...
