GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Chevrolet C-Series Medium Duty Truck B7 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 DTC P1112

Circuit Description

The intake air temperature (IAT) sensor contains a semiconductor device, a thermistor, which changes the resistance based on the temperature. The IAT sensor is located within the mass air flow (MAF) sensor. The IAT sensor has a signal circuit and a ground circuit. The powertrain control module (PCM) applies 5 volts on the signal circuit to the sensor. The PCM monitors the changes in this voltage caused by changes in the resistance of the sensor in order to determine intake air temperature.

When the intake air is cold, the sensor or thermistor resistance is high. The PCM signal voltage only pulls down a small amount through the sensor to a ground. Therefore, the PCM senses a high signal voltage or low temperature. When the intake air is warm, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the PCM senses a low signal voltage, or 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 P0102, P0103, P0117, P0118, P0500, P0502, or P0503 are not set.
    • The engine coolant temperature (ECT) is less than 135°C (275°F).
    • The engine run time is more than 30 seconds.
    • The vehicle speed is more than 40 km/h (25 mph).

Conditions for Setting the DTC
    • The IAT is more than 139°C (282°F).
    • The intermittent condition exists for a total of 5.5 seconds during a 100-second time period.

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • 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 non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Diagnostic Aids

If the engine sat overnight, the ECT and IAT 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 .

For an intermittent, refer to Intermittent Conditions .

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.

    2.

  2. This step inspects for proper connections.

  3. This step inspects the wiring harness.

    4.

  4. Using the Freeze Frame/Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/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 or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Install a scan tool.
  2. Idle the engine.
  3. Monitor the DTC Information option using the scan tool.

Is DTC P0112 also set?

Go to DTC P0112

Go to Step 3

3

  1. Turn ON the ignition, with 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 you move 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, with the engine OFF.
  2. Review the Freeze Frame/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 damaged connectors and terminals. Refer to Connector Repairs in Wiring Systems.

Is the action complete?

Go to Step 9

--

7

Repair the circuit as necessary. 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 and component if all of the circuits have been tested thoroughly and no faults can be found.

Is the action complete?

Go to Step 9

--

9
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 10

Go to Step 2

10

Use a scan tool. in order to observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK