Toyota Tundra. Manual — part 1165

Fig. 61: Intake Air Temperature Graph

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. 61).

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.

HINT:

When any of DTCs P0110, P0112 and P0113 are set, the ECM enters fail-safe mode. During fail-safe mode, the
IAT is estimated to be 20°C (68°F) by the ECM. Fail-safe mode continues until a pass condition is detected.

DTC TROUBLE DETECTION CONDITION CHART

DTC

No.

DTC Detection Condition

Trouble Area

P0110

Open or short in IAT sensor circuit for 0.5 seconds (1 trip
detection logic)



Open or short in IAT sensor
circuit



IAT sensor (built into MAF
meter)



ECM

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

HINT:

When any of these DTCs are set, check the IAT by entering the following menus: Powertrain/Engine and
ECT/All Data/Intake Air.

TEMPERATURE CHART

MONITOR DESCRIPTION

The ECM monitors the sensor voltage and uses this value to calculate the IAT. When the sensor output voltage
deviates from the normal operating range, the ECM interprets this as a malfunction in the IAT sensor and sets a
DTC.

Example:

If the sensor output voltage is more than 4.91 V for 0.5 seconds or more, the ECM determines that there is an
open in the IAT sensor circuit, and sets DTC P0113. Conversely, if the output voltage is less than 0.18 V for 0.5
seconds or more, the ECM determines that there is a short in the sensor circuit, and sets DTC P0112.

If the malfunction is not repaired successfully, a DTC is set 0.5 seconds after the engine is next started.

MONITOR STRATEGY

MONITOR STRATEGY

P0112

Short in IAT sensor circuit for 0.5 seconds (1 trip detection
logic)



Short in IAT sensor circuit



IAT sensor (built into MAF
meter)



ECM

P0113

Open in IAT sensor circuit for 0.5 seconds (1 trip detection
logic)



Open in IAT sensor circuit



IAT sensor (built into MAF
meter)



ECM

Temperature Displayed

Malfunction

-40°C (-40°F)

Open circuit

140°C (284°F) or higher

Short circuit

Related DTCs

P0110: IAT sensor range check (Fluctuating)
P0112: IAT sensor range check (Low voltage)
P0113: IAT sensor range check (High voltage)

Required Sensors/Components (Main)

IAT sensor

Required Sensors/Components (Related)

-

Frequency of Operation

Continuous

Duration

0.5 seconds

MIL Operation

Immediate

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

P0110:

TYPICAL MALFUNCTION THRESHOLDS

P0112:

TYPICAL MALFUNCTION THRESHOLDS

P0113:

TYPICAL MALFUNCTION THRESHOLDS

COMPONENT OPERATING RANGE

COMPONENT OPERATING RANGE

WIRING DIAGRAM

Sequence of Operation

None

Monitor runs whenever following DTCs not present

None

IAT sensor voltage

Less than 0.18 V, or more than 4.91 V

IAT sensor voltage [IAT]

Less than 0.18 V [More than 140°C (284°F)]

IAT sensor voltage [IAT]

More than 4.91 V [Less than -40°C (-40°F)]

IAT sensor voltage [IAT]

0.18 to 4.91 V [-40 to 140°C (-40 to 284°F)]

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

Fig. 62: Intake Air Temperature Wiring Diagram

INSPECTION PROCEDURE

HINT:

Read freeze frame data using the Techstream. Freeze frame data records the engine condition when
malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was
moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data
from the time the malfunction occurred.

1. READ OUTPUT DTC

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch ON and turn the Techstream ON.

c. Enter the following menus: Powertrain/Engine and ECT/Trouble Codes.

d. Read the DTCs.

Result

RESULT CHART

B : Go to step 5

C : Go to step 3

A : Go to next step

2. READ VALUE USING TECHSTREAM (INTAKE AIR TEMPERATURE)

a. Connect the Techstream to the DLC3.

b. Turn the ignition switch ON.

c. Turn the Techstream ON.

d. Enter the following menus: Powertrain/Engine and ECT/All Data/Intake Air.

e. Read the value displayed on the Techstream.

Standard:

Same as actual Intake Air Temperature (IAT).

Result

Display (DTC Output) Proceed To

P0110

A

P0112

B

P0113

C

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra