Circuit DescriptionThe intake manifold 1 temperature sensor is a variable resistor sensor and is used to measure the temperature of the air entering the intake manifold of the engine. The engine intake manifold temperature value is used by the electronic control module (ECM) for the engine protection system and engine emissions control.

The ECM supplies 5 volts to the intake manifold temperature signal circuit, and monitors the change in voltage caused by changes in the resistance of the sensor to determine the intake manifold temperature. When the intake air is cold, the sensor (or thermistor) resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to a ground, therefore, the ECM senses a high signal voltage or a low temperature. When the intake air is warm, the sensor resistance is low. The signal voltage pulls down a large amount, therefore, the ECM senses a low signal voltage, or a high temperature.

Component LocationThe intake manifold air temperature sensor is located in the air intake manifold.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault CodesThe ECM detects that the intake manifold temperature signal voltage is greater than 4.95-VDC for more than 10 seconds.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE light and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.A default value is used for the intake manifold temperature reading.Diesel exhaust fluid injection into the aftertreatment system is disabled.Active and stationary regeneration of the diesel particulate filter will be disabled.The exhaust gas recirculation valve will be closed.Conditions for Clearing the Fault CodeTo validate the repair, start the engine and let it idle for 1 minute.The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.For On-Board Diagnostics (OBD) engines, the ECM will turn off the MIL after three consecutive trips where the diagnostic runs and passes.The ?Reset All Faults? command in INSITE? electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD engines.

Shop TalkThe intake manifold air temperature sensor shares return wires in the engine harness with other sensors. Opens and shorts in the engine harness can cause multiple fault codes to be active. Check active fault codes with multiple counts first.

Possible causes of this fault code include:

Open return circuit in the harness, connectors, or sensorOpen signal circuit or shorted to voltage source

Possible Cause:1) ECM failure2) Engine Harness