Circuit DescriptionThe variable geometry turbocharger (VGT) is electronically activated by the VGT actuator. The VGT actuator is a smart device and receives information via the J1939 data link from the primary engine control module (ECM). The VGT actuator performs its own diagnostics and reports malfunctions back to the primary engine ECM, using the J1939 data link. The ECM then decodes the error message and converts it to a fault code. Component LocationThe VGT actuator is located on the turbocharger bearing housing. Conditions for Running the DiagnosticsThis diagnostic runs when the keyswitch is initially turned to the ON position. The keyswitch...

Circuit DescriptionThe fan control circuit is a device used by the engine to control the fan operation. When the engine control module (ECM) energizes the fan control circuit, the engine fan is engaged. The fan control circuit utilizes a pulse width modulated (PWM) signal. A PWM signal is a pulsed voltage signal between 0-VDC and system voltage. The frequency of the pulsed voltage signal is dependent on the application requirement. There are two types of fans supported by the fan control circuit; variable speed and ON/OFF. INSITE™ electronic service tool can be used to determine which fan type is presently...

Circuit DescriptionThe exhaust gas temperature is calculated by the engine control module (ECM). The exhaust gas temperature is derived by the ECM, based on engine operating conditions such as intake manifold air temperature, engine speed, injection timing, intake manifold pressure, and fuel flow. Component LocationThere is not a physical exhaust gas temperature sensor in the system. The exhaust gas temperature is a calculation of exhaust gas temperature before the turbocharger, and is also known as turbine intake temperature. Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is running. Conditions for Setting the Fault CodesThe Engine Control Module...

Circuit DescriptionThe air shutoff valve is an optional component used to shutdown the engine in the event of an engine overspeed condition. It can be closed via a manual shutdown switch or via an ECM command. Component LocationThe engine air shutoff valve location can vary depending on the OEM. Refer to the OEM service manual. Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running. Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the engine speed was greater than 2500 RPM for 0.25 seconds, or...

Circuit DescriptionThe ambient air temperature sensor is a variable resistor sensor and is used to measure the temperature of the ambient air. The engine control module (ECM) uses this temperature reading to optimize engine performance, and determine if heating of the SCR system is required. The engine control module (ECM) supplies 5 volts to the ambient air temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the ambient air temperature. Component LocationThe mounting location for the ambient air temperature sensor is OEM dependent. Refer to the appropriate OEM...