3UR-FE ENGINE CONTROL: SFI SYSTEM: DESCRIPTION (2008 Sequoia)

Last Modified: 11-29-2007		1.6 C
Service Category: Engine/Hybrid System	Section: Engine Control
Model Year: 2008	Model: Sequoia	Doc ID: RM000001WPH01LX
Title: 3UR-FE ENGINE CONTROL: SFI SYSTEM: DESCRIPTION (2008 Sequoia)

DTC

P0111

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 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.

DTC No.	DTC Detection Condition	Trouble Area
P0111	When either condition below is met: The intake air temperature change is small, from the previous trip warm-up to the following trip (2 trip detection logic). When the change in the intake air temperature after engine start is less than the threshold value.	Mass air flow meter assembly

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).

MONITOR STRATEGY

Related DTCs	P0111: Intake air temperature sensor rationality (After engine stop) P0111: Intake air temperature sensor rationality (After cold engine start)
Required Sensors/Components (Main)	Intake Air Temperature (IAT) sensor
Required Sensors/Components (Sub)	-
Frequency of Operation	Once per driving cycle
Duration	10 seconds or more
MIL Operation	2 driving cycles
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

All

Monitor runs whenever following DTCs are not present

None

After Engine Stop

Time after engine start	10 seconds or more
Battery voltage	10.5 V or more
ECT sensor circuit	OK
MAF sensor circuit	OK
ECT change since engine stop	-40°C (-40°F) or more
ECT before engine stop	70°C (158°F) or more
Accumulated MAF amount before engine stop	5752 g or more
Key-off duration	30 minutes

After Cold Engine Start

Key-off duration	5 hours
Time after engine start	10 seconds or more
ECT sensor circuit	OK
MAF sensor circuit	OK
ECT	70°C (158°F) or more
Accumulated MAF amount	5752 g or more
Either of the following conditions 1 or 2 is met:	-
1. Duration while engine load is low	120 seconds or more
2. Duration while engine load is high	10 seconds or more

TYPICAL MALFUNCTION THRESHOLDS

After Engine Stop

IAT change

Less than 1°C (2°F)

After Cold Engine Start

IAT change

Less than 1°C (2°F)

WIRING DIAGRAM

Refer to DTC P0110 .

INSPECTION PROCEDURE

PROCEDURE

1.	CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0111)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read DTCs.

Result

Result	Proceed to
P0111 and other DTCs are output	A
P0111 is output	B

HINT:

If any DTCs other than P0111 are output, troubleshoot those DTCs first.