GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Park Avenue 🢒 DTC 🢒 DTC P1112 Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage

Object Number: 571288 Size: SF
Engine Controls Components
Handling ESD Sensitive Parts Notice
Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The PCM applies 5 volts through a pull-up resistor to the IAT sensor. When the intake air is cold, the sensor resistance is high and the PCM will monitor a high signal voltage on the IAT signal circuit. If the intake air is warm, the sensor resistance is lower causing the PCM to monitor a lower voltage. DTC P1112 will set when the PCM detects an intermittently low signal voltage on the intake air temperature sensor signal circuit.

Conditions for Running the DTC
    • No active ECT sensor, MAF sensor or VSS DTCs are present.
    • The engine has been running for over 10 seconds.
    • Vehicle speed is more than 25 mph.

Conditions for Setting the DTC

IAT signal voltage intermittently indicates an intake air temperature more than 135°C (275°F).

Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC
    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction free warm-up cycles.
    • The PCM receives a clear code command from the scan tool.

Diagnostic Aids

Check for the following conditions:

    • Poor 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.
    • 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.
    • Skewed or mis-scaled IAT sensor. Refer to Temperature Versus Resistance .

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.

Test Description

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

  1. Verifies that the malfunction is present.

    2.

  2. If DTC P1112 can be repeated only by duplicating the Failure Records conditions, refer to 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.

DTC P1112 - IAT Sensor Circuit Intermittent Low Voltage

Step

Action

Values

Yes

No

1

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Select diagnostic trouble codes (DTC) info and note any other DTCs set.

Is DTC P0112 also set?

--

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

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.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems .

Was a problem found?

--

Go to Step 4

Go to Diagnostic Aids

4
  1. Review and record scan tool Failure Records data.
  2. Clear DTCs.
  3. Operate the vehicle within Failure Records conditions as noted.
  4. Using a scan tool, monitor specific DTC info for DTC P1112.

Does the scan tool indicate DTC P1112 failed?

--

Go to Step 2

System OK