P0111
DTC P0111 INTAKE AIR TEMPERATURE SENSOR 1 CIRCUIT RANGE/PERFORMANCEComponent Location:
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 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.
DTC DESCRIPTION
If the difference between actual and calculated value exceeds threshold value, the PCM judged this as a fault and DTC is set.
Specification:
Schematic Diagram:
SIGNAL WAVEFORM & DATA
This figure shows the wave form at terminal 3 of IATS at idle rpm.
1. 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
2. In case,when engine is cold,the output is below 0.5 V.
Possible cause Short between signal and ground line Bad PCM
The IATS and ECTS signals should be smooth and continuous without any sudden changes. When the engine is cold, the IATS and ECTS signals should look similar, depending on the ambient air temperature. Alter warm-up the IATS signal should not change significantly, while ECTS signal should drop. This indicates that the normal increase of the engine coolant temperature is larger than the normal increase of the intake air temperature as the engine warms up.
MONITOR DTC STATUS
This is the inspection procedure to determine whether it is present DTC or memoried one by monitoring the current signal or by using the function of oscilloscope with Hi-scan pro.
1. Connect scantool to Data Link Connector(DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor the "IATS signal" parameter on the scan tool.
NOTE: If the output voltage moves in reverse direction while air temperature changes, the IAT sensor is normal.
when IAT sensor is in malfunction, the default value for IAT is 20.3 °C.
Service standard
0 °C(32 °F) : 4.0 - 4.4 V
20 °C(68 °F): 3.3 - 3.7 V
40 °C(104 °F): 2.5 - 2.9 V
80 °C(176 °F): 1.0 - 1.4 V
4. Is parameter displayed within specifications?
YES:
- Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared.
- Thoroughly check connectors for looseness, poor connection, bending, corrosion,contamination,deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO: Go to "W/Harness Inspection" procedure
TERMINAL & 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?
YES: Repair as necessary and go to "Verification of vehicle Repair procedure.
NO: Go to "Signal circuit inspection" procedure.
SIGNAL CIRCUIT INSPECTION
Checking open circuit of IATS signal line is to find whether there is open or short circuit in MAP harness.
1. Check for open in harness
1. Ignition "OFF"
2. Disconnect IAT sensor connector.
3. Ignition "ON" & Engine "OFF"
4. Measure voltage between terminal 3 of sensor harness connector and chassis ground.
Specification: approximately 5 V
5. Is measure voltage within Specification?
YES; Go to "Check for short to power in harness" as below.
NO:
- In case over 5 V: Short circuit to battery between IATS harness connector and PCM harness connector.
- In case 0 V: Open or short circuit between IATS harness connector and PCM harness connector.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure
NOTE: In case,when IATS connector is disconnected,the voltage of IATS terminal 3 is 0 V.
- Possible cause: Open or short between terminal 42 of PCM and Terminal 3 of IATS
2. Check for short to power in harness
1. Ignition "OFF"
2. Disconnect IAT sensor connector and ECM connector.
3. Ignition "ON" & Engine "OFF"
4. Measure resistance between terminal 2 and 3 of sensor harness connector.
Specification: infinite
5. Is measure resistance within Specification?
YES: Go to "Check for short to ground in harness" as below.
NO:
- Short circuit between MAP sensor power circuit and IATS signal circuit.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure
3. Check for short to ground in harness
1. Ignition "OFF"
2. Disconnect IAT sensor connector and ECM connector.
3. Ignition "ON" & Engine "OFF"
4. Measure resistance between terminal 4 of sensor harness connector and chassis ground.
5. Measure resistance between terminal 3 and 4 of sensor harness connector
Specification : infinite
6. Is measure resistance within Specification?
YES: Go to "Ground Circuit Inspection" procedure.
NO:
- Short circuit between IATS signal circuit and ground circuit.
- Short chassis ground between IATS harness connector and PCM harness connector.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure
GROUND CIRCUIT INSPECTION
When the ground line is open,PCM assumes the air temperature as -39 °C and outputs 5 V.
1. Ignition "OFF"
2. Disconnect IAT sensor connector.
3. Ignition "ON" & Engine "OFF"
4. Measure voltage or resistance between terminal 4 of sensor harness connector and chassis ground.
Specification below 0.5 V or below 1 Ohms
5. Is measure voltage or resistance within Specification?
YES: Go to "Component Inspection" procedure.
NO:
- Open circuit between IATS harness connector and PCM harness connector.
- Open circuit between PCM harness connector and chassis ground.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
NOTE: In case, when checking open ground circuit, the resistence is infinite.
- Possible cause: Open or short between terminal 36 of PCM and Terminal 4 of IA TS.
COMPONENT INSPECTION
1. Check IATS
Measuring the resistence of IAT sensor is to find whether the open circuit exists in the sensor's inner side.
1. Measure resistance between terminal 3 and 4 of sensor connector(To sensor side)
Specification: 20 °C(68 °F) : 2.0 - 3.0 kOhms
0 °C(176 °F) : 0.2 - 0.4 kOhms
2. Does each resistance indicate continuity circuit?
YES: Go to "Check PCM" as below.
NO:
- Open circuit IATS.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure
NOTE: The purpose to measure IAT resistence is to decide where open circuit exists and the method is to check continuity between IAT signal line and ground line.
2. Check PCM
The purpose of checking PCM is to determine whether there is any malfunction of PCM.
1. Ignition "OFF"
2. Connect Scantool and Engine "ON"
3. Select simulation function on scantool.
4. Simulate voltage at terminal 3 of AT sensor signal connector.
5. Verify IATS voltage to change while raising or lowering simulation voltage with scan tool within 0.5 - 3.5 V
Specification: If the data is changeable as simulation voltage changes, it's OK
6. Is IAT sensor signal value changed according to simulation voltage?
YES: Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO: Substitute with a knowngood PCM and check for proper operation. If the problem is corrected, replace PCM and then 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. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code (DTC) which has been diagnosed
2. Using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions
4. Monitor that all rediness test have been verified as "Complete"
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.