Component Location
Description
1. General Description
The Intake Air Temperature Sensor (IATS) is installed into the Manifold Absolute Pressure sensor (MAP). 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.
2. DTC Description
The ECM sets DTC P0112 if the ECM detects signal voltage lower than the possible range of a properly operating IATS.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
Monitoring Strategy | ? Signal check low | ? Open circuit in signal line ? Open circuit in ground line ? Bad IATS sensor ? Bad ECM |
Threshold value | ? Intake air temperature : < -38.25?(-36.85?) |
Enable Conditions | ? Time elapse after start : > 240s Idle No fuel cut |
Diagnostic Time | ? > 15sec |
MIL on condition | ? 0.2s |
Specification
Service standard |
0? (32?) : 4.0~4.4 V |
20?(68?) : 3.0~3.8 V |
40?(104?) : 2.5~3.0 V |
80?(176?) : 1.0~1.5 V |
Waveform inspection in oscilloscope mode
This inspection procedure is recommended when service data with scan tool in not enough.
Start engine and warm up to operating temperature.
Probe(+) : IAT sensor harness connector NO3.
Probe(-) : Chassis ground.
If the output voltage moves in reverse direction while air temperature changes,the IAT sensor is normal.
Specification
Service standard |
0? (32?) : 4.0~4.4 V |
20?(68?) : 3.0~3.8 V |
40?(104?) : 2.5~3.0 V |
80?(176?) : 1.0~1.5 V |
Schematic Diagram
Signal Waveform
This figure shows the waveform at terminal 3 of IATS at idle rpm.
The lower the temperature is, the closer the output voltage of IAT goes to 5 V.In case,when engine is warmed up,the output is 5 V.
Possible cause : Open signal and ground line,or sensor’s inner circuit open |
In case,when engine is cold,the output is below 0.5V
Possible cause : Short between signal and groun line Bad ECM |
Is sensor switching properly?
If the output voltage moves in reverse direction while air temperature changes,the IAT sensor is normal.
In case there is no symptom and wrong data but DTC is shown |
The problem may be intermittent so slightly shake the connector and harness vertically and horizontally to check if there is any data changes |
If the data changes normally, the problem was intermittent so erase DTC and verify the same DTC reoccure. Go to "Terminal and Connector inspection" procedure. |
In case there is symptom and wrong data with DTC |
Check open,short or connector’s connection for IATS. |
Check the deterioration of IATS performance. Go to "Circuit Inspection" procedure. |
Signal Waveform
This figure shows the waveform at terminal 3 of IATS at idle rpm.
The lower the temperature is, the closer the output voltage of IAT goes to 5 V.In case,when engine is warmed up,the output is 5 V.
Possible cause : Open signal and ground line,or sensor’s inner circuit open |
In case,when engine is cold,the output is below 0.5V
Possible cause : Short between signal and groun line Bad ECM |