DTC P1112 Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage


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Circuit Description

The Intake Air Temperature (IAT) sensor contains a semiconductor device which changes resistance based on temperature (a thermistor). The IAT sensor mounts 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 a voltage (about 5.0 volts) on the signal circuit to the sensor. The PCM monitors 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, and the PCMs signal voltage is only pulled down a small amount through the sensor to ground. The PCM senses a high signal voltage (low temperature). When the intake air is warm, the sensor resistance is low, and the signal voltage is pulled down a greater amount. This causes the PCM to sense a low signal voltage (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

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Diagnostic Aids

If the engine sat overnight, the engine coolant temperature and intake air temperature values should display within a few degrees of each other. If the temperatures are not within 3C (5F), refer to Temperature vs Resistance .

For an intermittent, refer to Symptoms .

Test Description

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

  1. If DTC P0112 failed this ignition, this indicates a hard failure is present. When a hard failure is present, both the hard and intermittent DTCs set.
  1. When moving related connectors, visually/physically inspect connectors for the following:
  1. When moving the related wiring harnesses, visually/physically inspect the wiring for the following:
  1. Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data 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. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616-A . Using this kit prevents any damage to the harness connector terminals.

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

2

Did DTC P0112 also set?

--

Go to DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage

Go to Step 3

3

  1. Turn ON the ignition leaving the engine OFF.
  2. Observe the affected sensor value on a scan tool while moving related harness connectors (at the component and the PCM).

Does the sensor value change abruptly while a related connector is being moved?

--

Go to Step 6

Go to Step 4

4

Observe the affected sensor value on a scan tool while moving the related wiring harnesses. Does the sensor value change abruptly while moving the related electrical harnesses?

--

Go to Step 7

Go to Step 5

5

  1. Turn ON the ignition leaving the engine OFF.
  2. Review the Freeze Frame and/or Failure Records data for this DTC and observe the parameters.
  3. Turn OFF the ignition for 15 seconds.
  4. Start the engine.
  5. Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in the Freeze Frame/Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
  6. Select the Diagnostic Trouble Code (DTC) option, the Specific DTC option, then enter the DTC number using the scan tool.

Does the scan tool indicate that this diagnostic failed this ignition?

--

Go to Step 8

Go to Diagnostic Aids

6

Repair the damage connectors/terminals following the Repair Procedures in Connector Repairs in Wiring Systems Is the action complete?

--

Go to Step 9

--

7

Repair the faulty wiring. Refer to Wiring Repairs in Wiring Systems. Is the action complete?

--

Go to Step 9

--

8

  1. Re-inspect all the related circuits and the connectors.
  2. Replace the sensor/component if all the circuits have been tested thoroughly and no faults can be found.

Is the action complete?

--

Go to Step 9

--

9

  1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
  2. Idle the engine at the normal operating temperature.
  3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 10

Go to Step 2

10

Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed?

--

Go to the applicable DTC table

System OK