The Intake Air Temperature Sensor (IATS) is installed into the Mass Air Flow Sensor (MAFS). The IATS uses a thermistor whose resistance changes with the temperature. The electrical resistance of the IATS decreases as the temperature increases, and increases as the temperature decreases. The 5 V power source in the ECM is supplied to the IATS via a resistor in the ECM. That is, the resistor in the ECM and the thermistor in the IATS are connected in series. When the resistance value of the thermistor in IATS changes according to the intake air temperature, the signal voltage also changes. Using this signal, the information of the intake air temperature, the ECM corrects basic fuel injection duration and ignition timing.
Checking output signals of IATS under detecting condition, if an ouput signal is intermittently below 0.1V, ECM sets P1112.
Item | Detecting Condition | Possible cause | |
DTC Strategy |
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This code detects a continuous short to ground in either the signal circuit or the sensor | 1. Poor connection 2. Short to ground in harness 3. IATS 4. ECM | |
Enable Conditions | Case 1 |
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Engine running state
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No Vehicle speed sensor fault
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Vehicle speed > 50kph(30mph) | |
Case 2 |
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Engine running time >120 sec.
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Time from IG "OFF" to IG "ON" > 360 min. | ||
Threshold value |
•
Intake air temperature sensor's voltage < 0.1V | ||
Diagnosis Time |
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Continuous (More than 10 seconds failure for every 20 seconds test) | ||
MIL On Condition |
•
NO MIL ON(DTC only) | ||
Temp. (℃) | Resistance (kΩ) | Temp. (℃) | Resistance (kΩ) |
-40 | 95.95 ~ 105.78 | 20 | 3.42 ~ 3.61 |
-20 | 27.4 ~ 29.77 | 40 | 1.43 ~ 1.5 |
0 | 9.08 ~ 9.72 | 60 | 0.66 ~ 0.69 |
10 | 5.49 ~ 5.83 | 80 | 0.33 ~ 0.34 |
Fig.1) Normal waveform of IATS at 43℃ (109℉)
Fig.2) Normal data of IATS(53℉) & ECTS & EOTS at ig on
Fig.3) Normal data of IATS(82℉) & ECTS & EOTS after warming up.
The output signals of IATS & ECTS change smoothly without any rapid changes. These 2 sensor have almost the same characteristic signal during the early period after start. It means that the temperatures of intake air and engine coolant are depended on the temperature of atmosphere. Meanwhile, During engine warm up the output signal of the ECT will change quicker than the IAT signal. even it may not change almost.
