Circuit Description
The Intake Air Temperature (IAT) sensor contains a device which changes the resistance based on the temperature (a thermistor). The IAT sensor is located in the air intake passage of the engine air induction system. The IAT sensor has a signal circuit and a ground circuit. The ECM applies a voltage (about 5.0 volts) on the signal circuit to the sensor. The ECM monitors any changes in this voltage caused by changes in the resistance of the sensor in order to determine the intake air temperature.
When the intake air is cold, the sensor (thermistor) resistance is high. Therefore, the ECM will sense a high signal voltage (low temperature). When the intake air is warm, the sensor resistance is low. This causes the ECM to sense a low signal voltage (high temperature).
When the ECM senses a signal voltage outside of the normal operating range of the sensor, this DTC will set.
Conditions for Running the DTC
The engine must be running for at least 3 minutes
Conditions for Setting the DTC
The IAT signal voltage indicates an intake air temperature that is greater than 139°C (282°F)
OR
| • | The IAT signal voltage indicates an intake air temperature that is less than -43°C (-45°F). |
| • | The above condition is met for at least 10 seconds. |
Action Taken When the DTC Sets
The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes. |
| • | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic. |
| • | The ECM battery voltage is interrupted. |
| • | The scan tool clears the MIL/DTC. |
Test Description
The number(s) below refer to the step numbers on the diagnostic table.
-
Determine if the circuit is currently malfunctioning.
-
Determine if the circuit is currently malfunctioning.
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Using the Freeze Frame data may aid in locating an intermittent condition. If the DTC cannot be duplicated, review the information in the Freeze Frame. Try to operate the vehicle within the same freeze frame conditions (the RPM, the MAF, the vehicle speed, the temperature etc.) that were noted. This process may help to recreate the malfunction.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Is the IAT above the specified value? | 139°C (282°F) | |||
Is the IAT below the specified value? | -43°C (-45°F) | |||
4 |
Is the IAT value affected by moving the harness or connectors? | -- | ||
Is this DTC set? | -- | Refer to Diagnostic Aids | ||
6 |
Is the IAT below the specified value? | -43°C (-45°F) | ||
7 |
Is continuity indicated? | -- | ||
8 |
Is the IAT above the specified value? | 139°C (282°F) | ||
9 | Jumper the IAT signal circuit to a known good ground. Is the IAT above the specified value? | 139°C (282°F) | ||
10 |
Is continuity indicated? | -- | ||
11 |
Is continuity indicated? | -- | ||
12 | Repair the harness/connections as necessary. Refer to Test Description. Is the action complete? | -- | -- | |
13 | Repair the signal circuit shorted to ground. Is the action complete? | -- | -- | |
14 | Repair the open/high resistance signal circuit. Is the action complete? | -- | -- | |
15 | Repair the open/high resistance ground circuit. Is the action complete? | -- | -- | |
16 | Check for a poor connection or poor terminal tension at the IAT sensor harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||
17 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | -- | |
18 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||
19 |
Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | -- | |
20 |
Is this DTC set? | -- | ||
21 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK |
