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:
Inspection
1. INSPECT VANE PUMP SHAFT AND BUSHING IN VANE PUMP FRONT HOUSING
(a) Using a micrometer, measure the outer diameter [a]
of the vane pump shaft with pulley.
(b) Using vernier calipers, measure the inner diameter
[b] of the vane pump front housing bushing.
(c) Calculate the oil clearance ...
Power steering fluid
Bleeding
1. BLEED POWER STEERING SYSTEM
(a) Check the fluid level (See page PS-2).
(b) Jack up the front of the vehicle and support it with
stands.
(c) Turn the steering wheel.
(1) With the engine stopped, turn the steering
wheel slowly from lock to lock several times.
(d) Lower the ...
Detection range of the sensors
Approximately 2.0 ft. (60 cm)
Approximately 2.8 ft. (85 cm)
Approximately 5.9 ft. (180 cm)
The diagram shows the detection
range of the sensors. Note that the
sensors cannot detect obstacles
that are extremely close to the
vehicle.
The range of the sensors may
change depending ...
