DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage. GMC Truck GMC P42 Commercial Chassis 1998

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC P42 Commercial Chassis 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage

MAF and IAT Sensors
Engine Controls (Cell 21: Engine Data Sensors 2)
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. The control module supplies the IAT sensor a reference voltage on the IAT sensor signal circuit and a ground circuit. When the IAT sensor resistance is high, indicating a cold sensor, the IAT sensor signal voltage remains near the supplied voltage and decreases the signal voltage as the sensor warms. The control module monitors the IAT sensor signal circuit in order to calculate the temperature of the air entering the engine.

This DTC is designed to detect intermittent high voltage signals on the IAT sensor signal circuit.

Conditions for Running the DTC

•	No active ECT sensor DTCs

•	No active VS sensor DTCs

•	No active MAF sensor DTCs

•	The vehicle speed is less than 2 mph (3 km/h).

•	The MAF is less than 250 g/s.

•	The coolant temperature is more than 85°C(185°F).

•	The engine has been running for more than 100 seconds.

Conditions for Setting the DTC

The IAT voltage is more than 4.9 volts for less than 1 second.

Action Taken When the DTC Sets

•	The control module stores the DTC in history after the first failure but will not illuminate the malfunction indicator lamp (MIL).

•	The control module records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC

•	A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles.

•	A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle.

•	Use the scan tool Clear Information function.

Diagnostic Aids

The IAT sensor indicates the temperature of the ambient air entering the throttle body. The scan tool displays the IAT as volts and temperature. The IAT temperature should read very close to the temperature of the outside air. The IAT sensor temperature should rise gradually as the engine warms up and the underhood temperature increases. This DTC could set if the IAT sensor ground circuit is intermittently open or the IAT sensor signal circuit is intermittently open or shorted to voltage. If the high IAT sensor voltage reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set. Also, a sensor may become skewed or mis-scaled. The Temperature vs. Resistance Value Table will help to detect a skewed sensor. Refer to Temperature vs Resistance .

An intermittent may be caused by any of the following conditions:

•	A poor connection

•	Rubbed through wire insulation

•	A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Test Description

The number below refers to the step number on the diagnostic table.

If the IAT sensor voltage is more than 4.9 volts, then the condition is present. Even though DTC P0113 did not set, this DTC is more comprehensive and may aid in diagnosis.

Step	Action	Value(s)	Yes	No
Important: Be sure to use the same diagnostic test equipment for all measurements.
1	Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used. 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	Install the scan tool. Turn ON the ignition leaving the engine OFF. Display the IAT sensor voltage. Is the IAT sensor voltage more than the specified value?	4.9 V	Go to DTC P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage	Go to Step 3
3	Turn OFF the ignition. Disconnect the IAT sensor harness connector. Inspect the IAT sensor harness connector and terminals. Did you find a problem?	--	Go to Step 6	Go to Step 4
4	Disconnect the VCM C2 and C3 connectors. Inspect the terminals and connectors. Did you find a problem?	--	Go to Step 6	Go to Step 5
5	Reconnect the VCM and IAT sensor harness connectors. Turn ON the ignition leaving the engine OFF. Check for an intermittent open or short to voltage in the IAT sensor signal circuit or IAT sensor ground circuit while moving the harness in various locations. Display the IAT sensor voltage while moving the harness. Did the voltage fluctuate?	--	Go to Step 6	Go to Diagnostic Aids
6	Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete?	--	Go to Step 7	--
7	Using the scan tool, clear the DTCs. Start the engine. Allow the engine to idle until the engine reaches normal operating temperature. Select DTC and the Specific DTC function. Enter the DTC number which was set. Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran. Does the scan tool indicate the diagnostic Passed?	--	Go to Step 8	Go to Step 2
8	Does the scan tool display any additional undiagnosed DTCs?	--	Go to the applicable DTC table	System OK