DTC P1111. GMC Truck GMC MD Steel Tilt (W Model) 2003

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2003 🢒 GMC MD Steel Tilt (W Model) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 DTC P1111

Circuit Description

The intake air temperature (IAT) sensor is a thermistor. The powertrain control module (PCM) 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 powertrain control module (PCM) monitors the IAT sensor signal circuit in order to calculate the temperature of the air entering the engine.

This diagnostic trouble code (DTC) is designed to detect intermittent high voltage signals on the IAT sensor signal circuit.

Conditions for Running the DTC

•	DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0502, P0503, P1114, and P1115 are not set.

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

•	The mass air flow (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 temperature is less than -35°C (-31°F) for less than 1 second.

Action Taken When the DTC Sets

•	The control module stores the DTC information into memory when the diagnostic runs and fails.

•	The malfunction indicator lamp (MIL) will not illuminate.

•	The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

•	The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

•	A current DTC Last Test Failed clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

•	Clear the DTC with a scan tool.

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 reading should be very close to the temperature of the outside air. The IAT temperature should rise gradually as the engine warms up and the underhood temperature increases. This DTC may 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 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 Versus 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 inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections 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 temperature is less than -39°C (-38°F) then the condition is present. Even though DTC P0113 did not set, this DTC is more comprehensive and may aid in diagnosis.

Step	Action	Values	Yes	No
Schematic Reference: Engine Data Sensors Master Electrical Component List Powertrain Control Module Description EVAP and EGR Controls Fuel Injector Controls OBD II Symbol Description Notice
Important: Be sure to use the same diagnostic test equipment for all measurements.
1	Did you perform the Diagnostic System Check-Engine Controls?	--	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Install the scan tool. Turn ON the ignition, with the engine OFF. Display the IAT sensor temperature. Is the IAT sensor temperature less than the specified value?	-39°C (-38°F)	Go to DTC P0113	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 PCM connectors containing the IAT sensor signal and low reference circuits. Inspect the terminals and connectors. Did you find a problem?	--	Go to Step 6	Go to Step 5
5	Reconnect the PCM and IAT sensor harness connectors. Turn ON the ignition, with the engine OFF. Check for an intermittent open or short to voltage in the IAT sensor signal circuit or IAT sensor low reference circuit while moving the harness in various locations. Display the IAT sensor temperature while moving the harness. Did the temperature 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 that was set. Operate the vehicle, within 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