GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 2001 🢒 Aurora 🢒 Engine 🢒 Engine Controls - 3.5L 🢒 DTC P1112

Circuit Description

The intake air temperature (IAT) sensor contains a semiconductor device which changes resistance based on temperature. The IAT sensor is located in the air intake passage of the engine air induction system. The IAT sensor has a signal circuit and a ground circuit. The powertrain control module (PCM) applies approximately 5 volts on the signal circuit to the sensor. The PCM monitors changes in this voltage caused by changes in the resistance of the sensor to determine intake air temperature.

When the intake air is cold, the sensor resistance is high, and the PCM signal voltage is only pulled down a small amount through the sensor to ground. Therefore, the PCM will sense a high signal voltage or a low temperature. When the intake air is warm, the sensor resistance is low, and the signal voltage is pulled down a greater amount. Therefore the PCM will sense a low signal voltage or a high temperature. If the PCM detects an excessively low IAT signal voltage intermittently, (a high temperature indication), this DTC will set.

Conditions for Running the DTC
    • DTCs P0117, P0118, P0125, P0502, P0503, P1114, or P1115 are not set.
    • The engine has been running for over 10 seconds.
    • The vehicle speed is more than 25 mph.

Conditions for Setting the DTC

IAT signal voltage intermittently indicates an intake air temperature more than 134°C (274°F).

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

Notice: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:

   • The PCM harness connectors
   • The electrical center fuse/relay cavities
   • The component terminals
   • The component harness connector
Using this kit will prevent damage caused by the improper probing of connector terminals.

Check for the following conditions:

    • A faulty connection at the PCM--Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
    • A damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT display on the scan tool while moving connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the malfunction.
    • A skewed or incorrectly calibrated IAT sensor--Refer to the Temperature Versus Resistance table .

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

If the problem is intermittent, refer to Intermittent Conditions .

Test Description

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

  1. This step verifies that the malfunction is present.

    2.

  2. If DTC P1112 can be repeated only by duplicating the Failure Records conditions, refer to the Temperature vs Resistance. The table may be used to test the IAT sensor at various temperatures to evaluate the possibility of a shifted sensor that may be shorted above or below a certain temperature. If this is the case, replace the IAT sensor.

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

Using the scan tool, select DTC Info, Last Test Fail and note any other DTCs that are set.

Is DTC P0112 also set?

Go to DTC P0112

Go to Step 3

3

  1. Check the IAT signal circuit between the IAT sensor connector and the PCM for an intermittent short to ground. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If a problem is found, repair as necessary. Refer to Connector Repairs or Wiring Repairs in Wiring Systems.

Was a problem found and corrected?

Go to Step 4

Go to Diagnostic Aids

4
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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 5

Go to Step 2

5

With a scan tool, 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