The Intake Air Temperature Sensor (IATS) is installed into the Manifold Absolute Pressure Sensor (MAPS). 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 PCM is supplied to the IATS via a resistor in the PCM. That is, the resistor in the PCM 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 PCM corrects basic fuel injection duration and ignition timing.
The purpose of this diagnosis is to detect a stuck intake air temperature signal. The diagnostic function checks whether after a variation of the calculated intake air temperature also a variation of the measured intake air temperature is detected.
PCM sets DTC P0111 when the variation of measured intake air temperature from engine start is smaller than threshold while variation of calculated intake air temperature by PCM is greater than threshold.
Item | Detecting Condition | Possible Cause | |
DTC Strategy |
•
Plausibility check | 1. Poor connection or damaged harness 2. Faulty IAT sensor | |
Enable Conditions | Case1 |
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Engine running
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Battery voltage
•
Failure not detected for DTC
•
Engine Coolant Temperature
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Coolant temperature at engine start - coolant temperature at engine at pervious driving cycle
•
Cumulative time for IAT signal increase check ( low load driving condition :air flow ＜ 20kg/h and vehicle speed ＜ 12.4 mile/hour)
•
Cumulative time for IAT signal decrease check (high load driving condition : air flow 40kg/h and vehicle speed ＞ 24.8 mile/hour | |
Case2 |
•
Ignition "ON"
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Battery voltage ≥ 6V
•
No Intake Air Temp.(IAT) sensor electrical error | ||
Threshold Value | Case1 |
•
Intake air temperature signal vatiation since Engine start ＜ Threshold versus Air temperature at start (35.6F … 104F)
•
Low start intake air temperature:failure if IAT variation ＜ 34.7F
•
Middle start intake air temperature:failure if IAT variation ＜ 34.7F
•
High start intake air temperature:failure if IAT variation ＜ 68F | |
Case2 |
•
IAT - IAT moving mean value ＞ 46.4F | ||
Diagnostic Time | Case1 |
•
Immediate | |
Case2 |
•
0.5 sec. | ||
MIL On Condition |
•
2 Driving Cycles | ||
Temp.(℃) | Temp.(℉) | Resistance(㏀) | Temp.(℃) | Temp.(℉) | Resistance(㏀) |
-10 | 14 | 8.5 ~9.7 | 20 | 68 | 2.3 ~ 2.5 |
0 | 32 | 5.4 ~ 6.1 | 30 | 86 | 1.6 ~ 1.7 |
10 | 50 | 3.5 ~ 3.9 | 80 | 176 | Approx. 0.3 |
