Circuit Description
The DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage diagnostic monitors the signal circuit value. The IAT sensor is a variable resistor that measures the temperature of the intake air. The powertrain control module (PCM) supplies 5 volts to the IAT signal circuit and supplies a ground to the low reference circuit. If the PCM detects a low IAT signal voltage, which is a high temperature indication, this DTC sets.
The following table illustrates the difference between temperature, resistance, and voltage:
IAT | IAT Resistance | IAT Signal Voltage |
|---|---|---|
Cold | High | High |
Warm | Low | Low |
DTC Descriptor
This diagnostic procedure supports the following DTC.
DTC P0112 Intake Air Temperature (IAT) Sensor 1 Circuit Low Voltage
Conditions for Running the DTC
| • | The ignition is ON. |
| • | DTC P0113 is not set. |
| • | DTC P0112 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The PCM detects that the intake air temperature (IAT) sensor signal voltage is 0.08 volts or less. |
| • | The above condition is present for at least 5 seconds. |
Action Taken When the DTC Sets
| • | The powertrain control module (PCM) illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
| • | Use the Temperature vs Resistance table in order to test the IAT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the engine coolant temperature and the intake air temperature values should display within a few degrees. If the temperatures are not within 3°C (5°F), refer to Temperature Versus Resistance - Intake Air Temperature Sensor . |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if a condition is present.
-
An intake air temperature below -30°C (-22°F) indicates the PCM and the IAT wiring are OK.
-
Disconnecting the PCM allows using the DMM in order to check continuity of the circuits. This aids in locating an open or a shorted circuit.
-
After replacing the PCM a new minimum throttle position and idle speed must also be established.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Does the scan tool indicate that the IAT sensor is more than specified value? | 168°C (334°F) | Go to Step 4 | Go to Step 3 | |
3 |
Does the DTC fail this ignition cycle? | -- | Go to Step 4 | Go to Diagnostic Aids |
Does the scan tool indicate that the IAT sensor is at the specified value? | -40°C (-40°F) | Go to Step 6 | Go to Step 5 | |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 | |
6 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor 1 Replacement Did you complete the replacement? | -- | Go to Step 8 | -- |
Did you complete the replacement? | -- | Go to Step 8 | -- | |
8 |
Does the DTC run and pass? | -- | Go to Step 9 | Go to Step 2 |
9 | With a scan tool, select Capture Info in order to observe the stored information. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
