DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage. Oldsmobile Intrigue 1999

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1999 🢒 Intrigue 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage

Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice

Circuit Description

The intake air temperature (IAT) sensor is a thermistor that measures the temperature of the air entering the engine. The powertrain control module (PCM) applies 5 volts to the IAT sensor through a pull-up resistor. When the intake air is cold, the sensor resistance is high and the PCM monitors 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 is set when the PCM detects an intermittently high signal voltage on the IAT sensor signal circuit.

Conditions for Running the DTC

No engine coolant temperature (ECT) sensor, mass air flow (MAF) sensor or vehicle speed sensor (VSS) DTCs are present
The engine is running for over 3 minutes.
The ECT is more than 60°C (140°F).
The vehicle speed is less than 35 mph.

Conditions for Setting the DTC

The IAT signal voltage intermittently indicates an IAT of less than -34°C (-29°F).

Action Taken When the DTC Sets

The PCM stores the conditions which were present when the DTC set as Fail Records data only.

Conditions for Clearing the MIL/DTC

•	A history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.

•	DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids

Inspect for the following conditions:

•	A faulty connection at the PCM or the IAT sensor. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections.

•	Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT display on a scan tool while moving the connectors and wiring harnesses related to the IAT sensor. A change in the IAT display indicates the location of the malfunction.

•	A skewed or mis-scaled IAT sensor. Refer to Temperature vs Resistance .

Reviewing the Fail 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.

DTC P1111 - IAT Sensor Circuit Intermittent High Voltage

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	Use a scan tool in order to select DTC info, Last Tst 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	Inspect for a faulty sensor ground circuit connection at the intake air temperature (IAT) sensor. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found?	--	Go to Step 9	Go to Step 4
4	Inspect for a faulty IAT signal circuit terminal connection at the IAT sensor. If a problem is found, repair as necessary. Refer to Connector Repairs in Wiring Systems. Was a problem found?	--	Go to Step 9	Go to Step 5
5	Test the IAT signal circuit between the IAT sensor connector and the PCM for an intermittent open. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found?	--	Go to Step 9	Go to Step 6
6	Test the IAT signal circuit between the IAT sensor connector and the PCM for an intermittent short to voltage. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found?	--	Go to Step 9	Go to Step 7
7	Inspect for a faulty sensor ground circuit terminal connection at the PCM. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found?	--	Go to Step 9	Go to Step 8
8	Test for an intermittent open in the sensor ground circuit. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found?	--	Go to Step 9	Go to Diagnostic Aids
9	Review and record the scan tool Fail Records data. Clear any DTCs. Operate the vehicle within the Fail Records conditions as noted. Use the scan tool in order to monitor the Specific DTC info for DTC P1111. Does the scan tool indicate DTC P1111 Failed This Ign?	--	Go to Step 2	System OK