GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Grand Prix 🢒 DTC 🢒 DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage

Object Number: 388513 Size: SF
Cell 20: Power, Ground, MIL, and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts 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 5.0 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 P1111 will set when the PCM detects an intermittently high signal voltage on the intake air temperature sensor signal circuit.

Conditions for Running the DTC
    •  The engine has been running for over 3 minutes.
    • The engine coolant temperature is greater than 60°C (140°F).
    • The mass air flow is less than 12 g/s.
    •  Vehicle speed is less than 35 mph.

Conditions for Setting the DTC
    •  IAT signal voltage indicates an intake air temperature intermittently less than -33°C (-27°F).
    •  The conditions is present for up to 5 seconds.

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:

Important: :  Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

    •  Poor terminal connection.
         Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems.
    •  Damaged harness.
         Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems.
    •  Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain on Board Diagnostic System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Select DTC info, Last Test Fail and note any other DTCs set.

Is DTC P0113 also set?

--

Go to DTC P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage

Go to Step 3

3

Is DTC P1106, P1115, and/or P1121 also set?

--

Go to Step 6

Go to Step 4

4
  1. Check for a poor sensor ground circuit terminal connection at the IAT sensor.
  2. If a problem is found, repair as necessary. Refer to Testing for Continuity Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs .

Was a problem found?

--

Go to Step 10

Go to Step 5

5
  1. Check for a poor IAT signal circuit terminal connection at the IAT sensor.
  2. If a problem is found, repair as necessary. ssary. Refer to Testing for Continuity Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs .

Was a problem found?

--

Go to Step 10

Go to Step 6

6
  1. Check the IAT signal circuit between the IAT sensor connector and the PCM for an intermittent open.
  2. If a problem is found, repair as necessary. ssary. Refer to Testing for Continuity Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs .

Was a problem found?

--

Go to Step 10

Go to Step 7

7
  1. Check the IAT signal circuit between the IAT sensor connector and the PCM for an intermittent short to voltage.
  2. If a problem is found, repair as necessary. ssary. Refer to Testing for Continuity Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs .

Was a problem found?

--

Go to Step 10

Go to Step 8

8
  1. Check for a poor sensor ground circuit terminal connection at the PCM.
  2. If a problem is found, repair as necessary. ssary. Refer to Testing for Continuity Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs .

s a problem found?

--

Go to Step 10

Go to Step 9

9
  1. Check for an intermittent open or a faulty splice in the sensor ground circuit.
  2. If a problem is found, repair as necessary. ssary. Refer to Testing for Continuity Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs .

ound?

--

Go to Step 10

Go to Diagnostic Aids

10
  1. Review and record scan tool Fail Records data.
  2. Clear DTCs.
  3. Operate vehicle within Fail Records conditions as noted.
  4. Using a scan tool, monitor Specific DTC info for DTC P1111.

Does scan tool indicate DTC P1111 failed?

--

Go to Step 2

System OK