Circuit DescriptionThe exhaust gas pressure sensor is used to measure exhaust gas pressure in the exhaust manifold. This information is used by the engine control module (ECM) to control emissions and exhaust gas recirculation (EGR) valve operation. The ECM provides a 5 volt supply to the exhaust gas pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The exhaust gas pressure sensor provides a signal to the ECM on the exhaust gas pressure sensor signal circuit. This sensor signal voltage changes, based on the pressure in the exhaust manifold. Component LocationThe...

Lamp:Amber Reason:High voltage detected at the intake air heater signal circuit. Effect:The intake air heaters can be ON or OFF all the time. Circuit Description:The intake air heater improves starting and white smoke control in cold ambient conditions. The Engine Control Module (ECM) controls relays that switch power to the intake air heater. Air heaters on 12 volt systems will have two relays while 24 volt systems only require one relay. Component Location:The intake air heater is located at the air inlet connection to the intake manifold. The location of the intake air heater relays will vary by vehicle and...

Lamp:Amber Reason:Low voltage detected at the intake air heater signal circuit. Effect:The intake air heaters can be ON or OFF all the time. Circuit Description:The intake air heater improves starting and white smoke control in cold ambient conditions. The Engine Control Module (ECM) controls relays that switch power to the intake air heater. Air heaters on 12 volt systems will have two relays while 24 volt systems only require one relay. Component Location:The intake air heater is located at the air inlet connection to the intake manifold. The location of the intake air heater relays will vary by vehicle and...

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...

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 continuously when the keyswitch is in the ON position or when the...