GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1998 🢒 Aurora 🢒 DTC 🢒 DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage

Object Number: 191601 Size: SF
ESD Notice
Engine Controls Components
Cell 21: IAT, ECT, TP, MAP Sensors
OBD II Symbol Description Notice
ESD Notice

Circuit Description

The Intake Air Temperature (IAT) sensor is a thermistor, or variable resistor, that varies resistance based on temperature. Low temperature will result in a high signal voltage. If the IAT reading is -35°C (-30°F) or lower with the ECT sufficiently hotter than the IAT, the PCM sets DTC P1111.

Conditions for Running the DTC
    •  DTCs P0101, P0102, P0112, P0113, P0117, P0118, and P0502 not set.
    •  Engine speed 500 RPM or more for 10 seconds.
    •  MAF input 60 grams per second or less.
    •  Vehicle speed 50 MPH or less.
    •  5 seconds have passed with vehicle speed more than 7 MPH since the engine was started.
    •  Engine coolant temperature 0°C (32°F) or greater, or engine coolant temperature less than 0°C (32°F) and IAT at least 27°C (81°F) less than engine coolant temperature.

Conditions for Setting the DTC

IAT -35°C (-30°F) or less with the above test conditions met.

Action Taken When the DTC Sets
    •  The Malfunction Indicator Lamp (MIL) will not illuminate.
    •  No message will be displayed.

Conditions for Clearing the DTC
    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    • Use a scan tool to clear DTCs.
    • Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in Powertrain Control Module Description .

Diagnostic Aids

If fault is not present perform Powertrain Ground Check and also review Failure Rec. to determine conditions under which and how long ago the DTC set.

If a faulty sensor is suspected refer to Temperature vs Resistance table.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. If DTC P0111 is also set, diagnose it first because it may help to pinpoint a faulty IAT sensor.

    2.

  2. Checking for intermittent circuit faults that may cause a high IAT reading.

Step

Action

Value(s)

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

Turn the key ON.

Is DTC P0111 or P0113 also set?

--

Go to DTCs that are set

Go to Step 3

3

  1. Record fluid life indexes, turn the key to OFF and wait 30 seconds.
  2. Disconnect PCM connectors C1 and C2.
  3. Examine terminal 71 of C1 and terminal 76 of C2.
  4. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 4

4
  1. Disconnect IAT sensor connector.
  2. Examine terminals A and B.
  3. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 5

5
  1. Check the IAT sensor ground circuit and the IAT sensor signal circuit for possible opens or shorts to voltage.
  2. Repair circuits if needed. Refer to Wiring Repairs in Wiring Systems.

Was a repair made to any circuit?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Fault not present.

Go to Diagnostic Aids