Circuit Description
The intake air temperature (IAT) sensor is a thermistor that controls
signal voltage to the PCM. When the air is cold, the sensor resistance is
high, therefore the PCM will see a high signal voltage. As air warms,
sensor resistance becomes less and voltage drops.
Conditions for Running the DTC
| • | The PCM performs this DTC diagnostic continuously. |
| • | The ECT is less than 42.5°C (109°F). |
Conditions for Setting the DTC
| • | The intake air temperature is greater than or equal to 150°C
(302°F). |
| • | All of the diagnostic set conditions met for 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the
second consecutive drive trip that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic
fails. The first time the diagnostic fails, the Failure Records will store
this information. If the diagnostic reports a failure on the second
consecutive drive trip, the Freeze Frame records the operating conditions
at the time of failure and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after three consecutive trips without
a fault condition. |
| • | A History DTC will clear after forty consecutive warm-up cycles,
if this or any other emission related diagnostic does not report any failures. |
Diagnostic Aids
Important: Remove any debris from the PCM module connector surfaces before servicing
the PCM module. Inspect the PCM module connector gaskets when diagnosing/replacing
the module. Ensure that the gaskets are installed correctly. The gaskets
prevent contaminate intrusion into the PCM module.
Check harness routing for a potential short to ground in the signal
circuit. Refer to The scan tool displays intake air temperature in degrees
centigrade. A skewed sensor could result in poor driveability complaints.
An intermittent may be caused by one of the following:
| • | Rubbed through wire insulation. |
| • | Broken wire inside the insulation. |
