The DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage diagnostic monitors the IAT sensor signal. The IAT sensor is a thermistor, a variable resistor whose conductive value changes with temperature, in series with a fixed resistor in the powertrain control module (PCM). The PCM applies 5 volts to the IAT sensor. The PCM monitors the voltage across the IAT sensor and converts the voltage into a temperature reading. When the outside air temperature is cold, the IAT sensor resistance is high. When the outside air temperature is warm, the IAT sensor resistance is low. Therefore, when the air temperature is cold the PCM will receive a high voltage input, and when the air temperature is warm the PCM will receive a low voltage input.

The ignition is ON or the engine is running.

Check for any of the following conditions:

An intermittent malfunction may be caused by a fault in the IAT sensor circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If a DTC P0112 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool clear DTC information function. Road test the vehicle while monitoring the DTC P0112 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0112 appears in the Not Ran Since Code Cleared list, the DTC P0112 diagnostic has not yet run. When the DTC P0112 does not appear in the Not Ran Since Code Cleared list, the DTC P0112 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0112 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

If the DTC P0112 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step will determine if a fault is present.

3. Review the Freeze Frame data to determine when the DTC set. Always record this information.

4. This step determines if the fault is caused by a shorted signal return circuit or by a malfunctioning IAT sensor.

10. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0112 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0112 appears in the Not Ran Since Code Cleared list, the DTC P0112 diagnostic has not yet run. When the DTC P0112 does not appear in the Not Ran Since Code Cleared list, the DTC P0112 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0112 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.