GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2002 🢒 LeSabre 🢒 DTC 🢒 DTC P1112

Circuit Description

The intake air temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The powertrain control module (PCM) supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an intermittent low IAT signal voltage, indicating a high temperature, DTC P1112 sets.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0502, or P0503 are not set.
    • The engine run time is more than 10 seconds.
    • The vehicle speed sensor (VSS) indicates that vehicle speed is more than 40 km/h (25 mph).

Conditions for Setting the DTC

The intake air temperature (IAT) is more than 123°C (253°F) for 20 seconds.

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.

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

Observe the DTC Information with a scan tool.

Is DTC P0112 set?

Go to DTC P0112

Go to Step 3

3
  1. Test the IAT signal circuit between the IAT sensor and the PCM for an intermittent short to ground. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Connector Repairs or Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 4

Go to Intermittent Conditions

4
  1. Use the scan tool 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