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.
DTC DESCRIPTION
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 notchange PCM determines that a fault exists and a DTC is stored. MIL(Malfunction Indication Lamp) turns onwhen the malfunction lasts till cosecutive 2 driving cycle.
DTC DETECTING CONDITION
Item
Detection condition
Possible cause
DTC
Strategy
Case 1
●
Monitors the difference between the startup coolant andIAT values
●
IATS
Case 2
●
Monitors the difference between the startup IAT andcoolant values
Enable Conditions
Case 1
●
Engine soaked time ≥ 360min
●
Engine running state
●
No faults present
●
IAT stored previous trip
●
Startup Coolant Temperature＞ -20°C
●
Airflow ＞15 g/s
●
Vehicle speed ＞ 40kph
Case 2
●
Engine soaked time ≥ 360min
●
Engine running state
●
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
●
2 Driving Cycles
SIGNAL WAVEFORM AND DATA
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.
SPECIFICATION
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
SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1.
Check DTC Status
(1)
Connect scantool to Data Link Connector(DLC).
(2)
IG "ON".
(3)
Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu
(4)
Read "DTC Status" parameter.
(5)
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 codition then,go to " Component Inspection" procedure.
TERMINAL AND CONNECTOR INSPECTION
1.
Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
3.
Has a problem been found ?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure.
▶ Go to "Terminaal and connector inspection" procedure.
SIGNAL CIRCUIT INSPECTION
1.
IG "OFF" and disconnect IATS connector.
2.
IG "ON" and ENG "OFF"
3.
Measure voltage between terminal 4 of IATS harness connector and chassis ground.
Specification : Approx. 5V
4.
Is the measured voltage within specification ?
▶ Check short to battery in harness.
▶ If O.K, go to "Ground Circuit Inspection" procedure.
▶ If N.G, repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
▶ Repair open or short to ground in harness and go to "Verification of Vehicle Repair" procedure.
GROUND CIRCUIT INSPECTION
1.
IG "OFF" and disconnect IATS connector.
2.
Measure voltage terminal 4 of IATS harness connector and chassis ground.
3.
Measure voltage terminal 4 and 5 of IATS harness connector.
Specification : Voltage difference between measurement "A" and "B" is below 200mV.
4.
Is the measured voltage within specification ?
▶ Go to "Component Inspection" procedure.
▶ Repair contact resistance or open in harness and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1.
Check resistance of IATS
(1)
IG "OFF" and disconnect IATS connector.
(2)
Measure resistance between terminal 4 and 5 of IATS connector.(Component Side) after checking out the temperature of IAT with scantool
Specificaton :
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
(3)
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.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode
2.
Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3.
Read "DTC Status" parameter
4.
Is parameter displayed "History(Not Present) fault"?
▶ System performing to specification at this time. Clear the DTC.
