Es

Resistance

-20 0 20 40 60 80 100 (°C) -4 32 68 104 140 176 212 ("F)

Temperature

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. 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 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

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)

When any of these DTCs are set, check the IAT by selecting the following menu items on the intelligent tester: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / INTAKE AIR.

Temperature Displayed

Malfunctions

-40oC (-40oF)

Open circuit

140oC (284oF) or higher

Short circuit

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