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 5V 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, ignition timing correction and idle speed correction(Air-density correction).
Checking output signals of IATS every 20 sec. under detecting condition, if an ouput signal is below 0.1V for more than 10 sec., PCM sets P1112.
Item
Detecting Condition
Possible Cause
DTC Strategy
? This code detects a continuous short to ground in either the signal circuit or the sensor
? Poor Connection
? Short to ground in signal circuit.
? Faulty IATS
? Faulty PCM
Enable Conditions
Case 1
? Engine Run State
? No VSS Fault Active
? Vehicle Speed > 50kph(31mph)
? IAT Short Low Enable Criteria Met
Case 2
? Engine Running Time > 120sec.
? IG "OFF" time > 360min.
Threshold value
? IATS signal < 0.1V
Diagnosis Time
? Continuous (More than 10 sec. failure for every 20 sec. test)
MIL On Condition
? DTC only
Temp. (°C/°F)
Resistance (k?)
-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