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 engine control module (ECM) for the engine protection system and engine emission 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 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 engine intake manifold temperature sensor is located in the air intake manifold.

Conditions for Running the DiagnosticsThis diagnostic consists of two parts. The first part runs when the keyswitch is turned ON and before engine speed is detected. The ECM must not see a key cycle for a period of ten hours before this part of the diagnostic will run.

The second part runs when the engine is operating.

Conditions for Setting the Fault CodesThe ECM detects that the engine intake manifold temperature sensor reading is higher or lower than the other temperature sensors on the engine after an extended period of engine OFF time.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp and/or malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.The ECM will estimate engine intake manifold temperature.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 (EGR) valve will be closed.Engine torque will be reduced if the engine is operated for an extended period of time with this fault code active.Conditions for Clearing the Fault CodeTo validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop-and-go city driving and steady state highway driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.To validate the repair using a Chassis Dynamometer, utilize a routine that incorporates acceleration and motoring events, steady state highway operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passesFor On-Board Diagnostic (OBD) engines, the ECM will turn off the MIL after three consecutive trips where the diagnostic runs and passes.This fault code can also be cleared with INSITE? electronic service tool.The “Reset All Faults” command in INSITE? electronic service tool can be used to clear active and inactive fault codes, as well as extinguish the MIL for OBD applications.

Shop TalkPossible causes of this fault code include:

In-range malfunction of the engine intake manifold temperature sensorHigh resistance in the engine intake manifold temperature sensor signal or return lines.

Possible Cause:1) Ambient air temperature sensor failure2) ECM failure3) ECM calibration