P0112 Intake Air Temperature Sensor 1 Circuit Low input

COMPONENT LOCATION

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GENERAL DESCRIPTION
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
Checking output signals of IATS every 20 sec. under detecting condition, if an ouput signal is below 0.1V for more than 10 sec., ECM sets P0112.
DTC DETECTING CONDITION
 
ItemDetecting ConditionPossible Cause
DTC Strategy
This code detects a continuous short to ground in either the signal circuit or the sensor
1.
Poor connection
2.
Short to ground in harness
3.
IATS
4.
ECM
Enable
Conditions
Case 1
Engine running state
No Vehicle speed sensor fault
Vehicle speed > 50kph(30mph)
Case 2
Engine running time >120 sec
Time from IG “OFF” to IG “ON” > 360 min
Threshold value
Intake air temperature sensor’s voltage < 0.1V
Diagnosis Time
Continuous (More than 10 seconds failure for every 20 seconds test)
MIL On Condition
3 Driving Cycles

 

SPECIFICATION
 
Temp. (°C)Resistance (kΩ)Temp. (°C)Resistance (kΩ)
-4040.93 ~ 48.35202.31 ~ 2.57
-2013.89 ~ 16.03401.08 ~ 1.21
05.38 ~ 6.09600.54 ~ 0.66
103.48 ~ 3.90800.29 ~ 0.34

 

DIAGNOSTIC CIRCUIT DIAGRAM

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SIGNAL WAVEFORM & DATA

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Fig.1) Normal data of IATS & ECTS & EOTS at ig on
Fig.2) Normal data of IATS & ECTS & EOTS after warming up.
Fig.3) Normal waveform of IATS
 
The output signals of IATS & ECTS change smoothly without any rapid changes. These 2 sensor have almost the 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 engine warm up the output signal of the ECT will change quicker than the IAT signal. even it may not change almost.

 

MONITOR GDS DATA
1.
Connect GDS to Data Link Connector(DLC).
2.
IG “ON”.
3.
Select “DTC” button, and then Press “DTC Status” to check DTC’s information from the DTCs menu.
4.
Read “DTC Status” parameter.

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5.
Is parameter displayed “Present fault”?
 

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â–¶ Go to “Terminal and Connector inspection” procedure.

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▶ Fault is intermittent caused by poor contact in the sensor’s and/or ECM’s connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary

 

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?
 

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â–¶ Repair as necessary and go to “Verification of Vehicle Repair” procedure .

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â–¶ Go to ” Signal Circuit Inspection ” procedure.

 

SIGNAL CIRCUIT INSPECTION
â–  Check voltage
1.
IG “OFF” and disconnect IATS connector.
2.
IG “ON”
3.
Measure voltage between signal terminal of IATS harness connector and chassis ground.
 Approx. 3.3V

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4.
Is the measured voltage within specification ?
 

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â–¶ Go to “Component Inspection” procedure.

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â–¶ Go to “Check short to ground in harness” procedure.

 

â–  Check short to ground in harness
1.
IG “OFF” and disconnect IATS connector and ECM connector.
2.
Measure resistance between signal terminal of IATS harness connector and chassis ground.(Measurement “A”)
3.
Measure resistance between signal and ground terminals of IATS harness connector.(Measurement “B”)
4.
Measure resistance between signal terminal of IATS harness connector and ground terminal of Baro Sensor harness connector.(Measurement “B”)
 Infinite

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5.
Is the measured resistance within specification ?
 

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â–¶ Go to “Component Inspection” procedure.

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â–¶ Repair short to ground in harness
COMPONENT INSPECTION
â–  Check IATS resistance
1.
IG “OFF” and disconnect IATS connector.
2.
Measure resistance between signal and ground terminals of IATS connector after checking out the temperature of IATS with GDS (Component Side)
Specification :
 
Temp. (°C)Resistance (kΩ)Temp. (°C)Resistance (kΩ)
-4040.93 ~ 48.35202.31 ~ 2.57
-2013.89 ~ 16.03401.08 ~ 1.21
05.38 ~ 6.09600.54 ~ 0.66
103.48 ~ 3.90800.29 ~ 0.34

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3.
Is the measured resistance within specification ?
 

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â–¶ Substitute with a known – good ECM and check for proper operation. If the problem is corrected, replace ECM and go to “Verification of Vehicle Repair” procedure.
   
 
There is a memory reset function on GDS that can erase optional parts automatically detected and memorized by ECM. Before or after testing ECM on the vehicle, use this function to reuse the ECM on the others

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â–¶ Substitute with a known – good IATS and check for proper operation. If the problem is corrected, replace IATS

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