Circuit Description
The Intake Air Temperature (IAT) sensor is a thermistor located in the fresh air duct to the throttle body in order to monitor the temperature of the air entering the throttle body. The VCM applies 5 volts to the sensor on the 5 volt reference circuit. When the air is cool, the resistance in the sensor measures high and the VCM senses a high voltage signal. If the air is warm, the sensor resistance measures low and the VCM senses a low voltage signal. This DTC is a type A DTC.
Conditions for Setting the DTC
The following items will set the DTC:
| • | No ECT sensor DTCs |
| • | No VS sensor DTCs |
| • | No MAF sensor DTCs |
| • | The vehicle speed less than 2 mph |
| • | The MAF is less than 250 grams per second |
| • | The engine coolant temperature greater than 84.7° C |
| • | The engine run time is greater than 100 seconds |
| • | The intake air temperature voltage greater than 4.9 |
Action Taken When the DTC Sets
The VCM turns the MIL ON when P0113 is reported and 1 failure has occurred.
Conditions for Clearing the MIL/DTC
The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.
Diagnostic Aids
A scan tool indicates the temperature of the ambient air which is entering the throttle body. The air temperature should read very close to the temperature of the outside air. The air temperature should rise gradually as the engine warms up and the underhood temperature increases. If DTC P1111 is set, the problem is intermittent. Check for an open in the IAT sensor circuit. This may be accomplished by moving the VCM harness at various locations and monitoring IAT temperature or IAT voltage on the scan tool. If the voltage varies, look for an open in the area of the harness that caused the variance. Also, a sensor may become skewed or mis-scaled. The Temperature vs. Resistance Value Table will help in order to detect a skewed sensor. Refer to Temperature vs Resistance .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Important: Use the same diagnostic test equipment for all the measurements.
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If the IAT sensor circuit voltage measures greater than 4.9 volts, the conditions for the DTC are still present, and the problem is not intermittent.
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This test will bypass the IAT sensor and will confirm that the IAT signal circuit and the sensor ground circuit to the VCM are sound. Grounding the signal circuit will provide a low voltage input to the VCM. The VCM should recognize this low voltage and indicate a high IAT temperature.
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This test determines if the IAT sensor signal circuit is okay. If the scan tool does not indicate a high temperature, the IAT signal circuit is open.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing DTCs, use the scan tool in order to record freeze frame and the failure records for reference because the Clear Info function will lose the data. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Is the IAT sensor voltage greater than the specified value? | 4.9 V | |||
Does the scan tool display a IAT sensor voltage less than the specified value? | 0.82 V | |||
Jumper the IAT sensor signal circuit to a known good ground. Does the scan tool display an IAT sensor voltage less than the specified value. | 0.82 V | |||
5 | Is the DTC P0123 also set? | -- | Go to DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage | |
6 | The DTC is intermittent. If no additional DTCs are stored, refer to the Diagnostic Aids. If the additional DTCs are stored, refer to those tables. | -- | Go to The Applicable DTC Table | |
7 | Inspect the sensor connector and the VCM connector for the proper connection. Was a problem found? | -- | ||
8 | Check the IAT sensor ground circuit for an open between the IAT sensor and the VCM. Was a problem found? | -- | ||
9 | Check the sensor signal circuit for an open between the IAT sensor and the VCM. Was a problem found? | -- | ||
10 | Repair the circuit as necessary. Refer to Wiring Repairs in Engine Electrical. Is the repair complete? | -- | -- | |
11 | Replace the IAT sensor. Refer to IAT Sensor Replacement . Is the replacement complete? | -- | -- | |
12 | Replace the VCM. Important: If the VCM is faulty, reprogram the VCM. Refer to VCM Replacement/Programming . Is the replacement complete? | -- | -- | |
13 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
14 | Using the scan tool, select the Capture Info and the Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to The Applicable DTC Table | System OK |
