Circuit Description
The intake air temperature (IAT) sensor contains a thermistor which changes the resistance based on the temperature. 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 PCM applies 5 volts on the signal circuit to the sensor. The PCM monitors the changes in this voltage that are caused by changes in the sensor resistance in order to determine the intake air temperature.
When the intake air is cold, the sensor resistance is high. The PCMs signal voltage is only pulled down a small amount through the sensor to ground. The PCM senses a high signal voltage, indicating a low temperature. When the intake air is warm, the sensor resistance is low. The signal voltage is pulled down more. The PCM senses a low signal voltage, indicating a high temperature.
When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0117, P0118, P0125, and P0503 are not set: |
| • | The engine run time is more than 30 seconds. |
| • | The vehicle speed at least 40 km/h (25 mph). |
| • | The engine coolant temperature (ECT) is more than 135°C (275°F). |
Conditions for Setting the DTC
| • | The intake air temperature is more than 139°C (282°F). |
| • | All conditions exist for 5 seconds. |
Action Taken When the DTC Sets
| • | 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. |
Conditions for Clearing the MIL/DTC
| • | 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. |
Diagnostic Aids
Important:
• Remove any debris from the PCM connector surfaces before servicing
the PCM. Inspect the PCM connector gaskets when you diagnose or replace the
PCM. Ensure that the gaskets are installed correctly. The gaskets
prevent contaminant intrusion into the PCM. • For any test that requires probing the PCM or component
harness connectors, use the J 35616
connector test adapter kit. Using this kit prevents
any damage to the harness connector terminals. Refer
to
Using Connector Test Adapters
in Wiring Systems.
If the engine has sat overnight, the engine coolant temperature and the intake air temperature values should display within a few degrees of each other. If the temperatures are not within 3°C (5°F), refer to Temperature Versus Resistance .
If you determine that the DTC occurs intermittently, performing the P1112 diagnostic table may isolate the cause of the fault. Refer to DTC P1112 .
For an intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies if the condition is present.
-
Using the Freeze Frame/Failure Records may help to locate an intermittent condition. If you cannot duplicate the DTC, the information in the Freeze Frame/Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions that you observed. These conditions include the following:
-
An IAT that is below -30°C (-22°F) indicates the PCM and the IAT wiring are OK.
-
Disconnecting the PCM allows you to use the DMM in order to test continuity of the circuits. This procedure helps to locate an open circuit or a shorted circuit.
| - | The RPM |
| - | The vehicle load |
| - | The vehicle speed |
| - | The temperature |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Is the IAT above the specified value? | 139°C (282°F) | Go to Step 4 | Go to Step 3 | |
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | |
Is the IAT at the specified value? | -39°C (-38°F) | Go to Step 6 | Go to Step 5 | |
Is the IAT signal circuit grounded? | -- | Go to Step 8 | Go to Step 7 | |
6 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | Go to Step 8 | -- |
7 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 8 | -- |
8 |
Does the DTC run and pass? | -- | Go to Step 9 | Go to Step 2 |
9 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
