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:
Installation
1. INSTALL IGNITION SWITCH ASSEMBLY
(a) Install the ignition switch with the 2 screws.
(b) Install the ignition switch connector.
2. INSTALL STEERING COLUMN COVER LOWER
(a) Attach the 4 claws to install the steering column
cover lower.
(b) Insert the key into the ignition key cylinde ...
Disassembly
1. REMOVE PROPELLER SHAFT ASSEMBLY
(a) Put matchmarks on both the flanges.
(b) Remove the 4 nuts, bolts and washers.
2. REMOVE INTERMEDIATE SHAFT
(a) Put matchmarks on the propeller shaft subassembly
and universal joint flange.
NOTICE:
Do not use a punch for the marks.
(b) Using a ...
Removal
NOTICE:
Before removing the tire pressure warning ECU, read the
registered transmitter IDs of all wheels and write them
down to use for re-registration of transmitter IDs (See
page TW-20).
1. DISCONNECT CABLE FROM NEGATIVE BATTERY
TERMINAL
CAUTION:
Wait at least 90 seconds after dis ...
