The Intake Air Temperature (IAT) sensor measures the temperature of engine intake air. The Intake Air Temperature (IAT) sensor is a thermistor (a variable resistor that changes along with outside air temperature) in series with a fixed resistor in the PCM. The PCM applies 5volts to the IAT sensor. The PCM monitors the voltage across the IAT sensor and converts it into a temperature reading. When the outside air temperature is cold the IAT sensor resistance is high, and when the outside air temperature is warm the IAT sensor resistance is low. Therefore, when the air temperature is cold the PCM will receive a high voltage input, and when the air temperature is warm the PCM will receive a low voltage input. The signal from IAT sensor is used for injection time correction (Cold post start correction), ignition angle correction(Air temperature correction) and idle speed correction(Air-density correction).
PCM monitors difference between the startup coolant and IAT values.
If the difference between the startup coolant and startup IAT exceeds a maximum allowed value, PCM determines that a fault exists and a DTC is stored.
Item | Detection condition | Possible cause | |
DTC Strategy | Case 1 | ● Skew Low Test: Monitors the difference between the startup coolant and IAT values | ● Poor Connection ● Open or short in harness ● IATS ● PCM |
Case 2 | ● Skew High Test: Monitors the difference between the startup IAT and coolant values | ||
Enable Conditions | Case 1 | ● Engine soaked time ≥ 360min ● Engine running state ● No disabling faults present ● IAT stored previous trip ● IAT Skewed Test Not Complete ● Startup Coolant Temperature >-20°C ● Airflow >15 g/s ● Vehicle speed >40kph | |
Case 2 | ● Engine soaked time ≥ 360min ● Engine running state ● No disabling faults present ● IAT stored previous trip ● IAT Skewed Test Not Complete ● Airflow >15 g/s ● Vehicle speed >40kph | ||
Threshold Value | Case 1 | ● Startup Coolant - Startup IAT ≥ 30°C | |
Case 2 | ● Startup IAT - Startup Coolant ≥ 20°C | ||
Diagnosis Time | ● Continuous (More than 1.25 second failure) | ||
MIL On Condition | ● 2 Driving Cycles |
Temp. (°C/°F) | Resistance (kΩ) | Temp. (°C/°F) | Resistance (kΩ) |
-40(-40) | 95.95 ~ 105.78 | 20(68) | 3.42 ~ 3.61 |
-20(-4) | 27.4 ~ 29.77 | 40(104) | 1.43 ~ 1.5 |
0(32) | 9.08 ~ 9.72 | 60(140) | 0.66 ~ 0.69 |
10(50) | 5.49 ~ 5.83 | 80(176) | 0.33 ~ 0.34 |
