The intake air temperature (IAT) sensor is a thermistor. The powertrain control module (PCM) supplies the IAT sensor a reference voltage on the IAT sensor signal circuit and a ground circuit. When the IAT sensor is cold, the resistance is high. The IAT sensor signal voltage remains near the supplied voltage and decreases the signal voltage as the sensor warms. The control module monitors the IAT sensor signal circuit in order to calculate the temperature of the air entering the engine.
This diagnostic trouble code (DTC) is designed to detect an IAT sensor signal voltage higher than possible in a normally operating IAT system.
• | DTCs P0117, P0118, P0125, P0502, or P0503 are not set. |
• | The engine run time is more than 320 seconds. |
• | The vehicle speed sensor indicates that vehicle speed is less than 24 km/h (15 mph). |
The IAT sensor signal voltage indicates that the intake air temperature is less than -40°C (-40°F) for 3 seconds.
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
• | When the vehicle is at ambient temperature, compare the IAT sensor to the engine coolant temperature (ECT) sensor. The IAT sensor and the ECT sensor should be relatively close to each other. |
• | Use the Temperature vs Resistance Values Table below to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance . |
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||
---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||
2 |
Does the scan tool indicate that the IAT sensor temperature is less than the specified value? | -38°C (-36°F) | Go to Step 4 | Go to Step 3 | ||||
3 |
Does the DTC reset? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||
Does the scan tool indicate IAT sensor is temperature more than the specified value? | 128°C (262°F) | Go to Step 5 | Go to Step 6 | |||||
5 | Measure the voltage from the signal circuit of the IAT sensor to a good ground. Does the voltage measure more than the specified value? | 5 V | Go to Step 9 | Go to Step 10 | ||||
6 |
Does the scan tool indicate IAT sensor temperature more than the specified value? | 128°C (262°F) | Go to Step 8 | Go to Step 7 | ||||
7 |
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 | ||||
8 | Repair the IAT low reference circuit for an open or high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- | ||||
9 | Repair the short to voltage in the IAT signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- | ||||
10 |
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 | ||||
11 |
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 | ||||
12 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
14 |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Step 2 | ||||
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTC's that you have not diagnosed? | -- | System OK |