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 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.
PCM monitors temperature changes resulting from soaking the vehicle. Therefore, Coolant temperature and Intake temperature should be changed. If PCM detects intake air temperature correlated to coolant temperature does not change PCM determines that a fault exists and a DTC is stored. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item | Detection condition | Possible cause | |
DTC Strategy | Case 1 | ● Monitors the difference between the startup coolant and IAT values | ● IATS |
Case 2 | ● Monitors the difference between the startup IAT and coolant values | ||
Enable Conditions | Case 1 | ● Engine soak time ≥ 360min ● Engine running ● No faults present ● IAT stored previous trip ● Startup Coolant Temperature ＞ -20°C ● Airflow ＞ 15 g/s ● Vehicle speed ＞ 40kph | |
Case 2 | ● Engine soak time ≥ 360min ● Engine running ● No faults present ● IAT stored previous trip ● Airflow ＞ 15 g/s ● Vehicle speed ＞ 40kph | ||
Thresh old 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 | ● No MIL ON (DTC only) | ||
Temp. (℃/℉) | Resistance (kΩ) | Temp. (℃/℉) | 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 |
The output signals of IATS ＆ ECTS change smoothly without any rapid changes. Those have almost 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 the warming up, the output signal of ECTS is going up increasingly. but, the output signal of IATS changes a little bit. even it may not change almost. It means that the heat of engine does not affect on the temperature of intake air.
Check DTC Status
Connect scantool to Data Link Connector(DLC).
IG "ON".
Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.
Read "DTC Status" parameter.
Is parameter displayed "Present fault"?
▶ Go to "Component Inspection" procedure.
▶ Fault is intermittent caused by PCM memory was not cleared after repair. Erase DTC and drive the vehicle to satisfy the enable condition then, go to " Component Inspection" procedure.
IG "OFF" and disconnect IATS connector.
Measure resistance between signal and ground terminals of IATS connector after checking out the temperature of IATS with scantool.
Temp. (℃/℉) | Resistance (kΩ) | Temp. (℃/℉) | 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 |
Is the measured resistance within specification ?
▶ Go to "Verification of Vehicle Repair" procedure.
▶ Substitute with a known - good IATS and check for proper operation. If the problem is corrected, replace IATS and go to "Verification of Vehicle Repair" procedure..
After a repair, it is essential to verify that the fault has been corrected.
Connect scantool and select "DTC" button.
Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
Read "DTC Status" parameter
Is parameter displayed "History(Not Present) fault"?
▶ System performing to specification at this time. Clear the DTC
▶ Go to the applicable troubleshooting procedure.
