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. REMOVE TRANSFER CASE NO.1 PLUG (See page
TF-8)
2. REMOVE TRANSFER DRAIN PLUG
(a) Remove the transfer drain plug, drain gasket and
bleed transfer oil.
3. REMOVE EXHAUST PIPE ASSEMBLY
HINT:
(See page EX-8)
4. REMOVE PROPELLER WITH CENTER BEARING
SHAFT ASSEMBLY
HINT:
(See page PR-3)
5. R ...
Data list / active test
1. DATA LIST
HINT:
Using the DATA LIST displayed on the intelligent tester,
you can read the value of the switch, sensor, actuator,
etc. without parts removal. Reading the DATA LIST as
the first step of troubleshooting is one way to shorten the
labor time.
Connect the intelligent tester to ...
Taking out the spare tire
Slide the front passenger’s seat to the frontmost lock position and
the right side second seat to the rearmost lock position so they will
not interfere with the jack handle.
Open the right side sliding door
and you will find the flap on the
floor. Pull back the flap to find
the ...
