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Reason:Aftertreatment SCR Catalyst Conversion Efficiency – Data Valid But Below Normal Operating Range – Moderately Severe Level. NOx conversion across the SCR catalyst is too low. Effect:Possible reduced engine performance. Circuit Description:The engine control module (ECM) monitors the NOx concentration in the engine’s exhaust gases using an aftertreatment intake NOx sensor and an aftertreatment outlet NOx sensor. By comparing these two values, the ECM is able to determine the conversion efficiency of the SCR catalyst and dosing system. Component Location:The SCR catalyst is located in the vehicle’s exhaust system, after the diesel particulate filter and decomposition tube. Conditions for Running...

Reason:Aftertreatment Outlet NOx Sensor Heater – Abnormal Rate of Change. The aftertreatment outlet Nox sensor heater is unable to maintain its normal operating temperature. Effect:None on performance. Circuit Description:The aftertreatment outlet NOx (nitrogen oxides) sensor is a smart device and communicates with the engine control module (ECM) via the J1939 data link. The aftertreatment outlet NOx sensor performs its own internal diagnostics and reports malfunctions back to the primary ECM using the J1939 data link. The NOx sensor is permanently attached to the NOx control module. They are serviced as a single component and can not be replaced individually. The...

Reason:Aftertreatment Diesel Exhaust Fluid Pressure Sensor – Data Erratic, Intermittent, or Incorrect. The diesel exhaust fluid pressure sensor has reported a reading too high or low for the operating conditions. Effect:Possible reduced engine performance. Circuit Description:The Engine Control Module (ECM) provides a 5 volt supply and a ground to the aftertreatment diesel exhaust fluid pressure sensor. The pressure sensor provides a signal to the ECM on the sensor signal circuit. This sensor signal voltage changes, based on the aftertreatment diesel exhaust fluid pressure supplied by the dosing unit. The ECM will detect a low signal voltage at low diesel exhaust...

Reason:Engine VGT Nozzle Position – Mechanical System Not Responding or Out of Adjustment. The smart VGT controller has detected incorrect stop limits or the VGT is unable to move to the closed position. Effect:Possible reduced engine performance. Circuit Description:The 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...

Reason:Engine Fan Clutch 2 Control Circuit – Voltage Above Normal or Shorted to High Source. Open circuit or high voltage detected at the fan control circuit. Effect:The fan can stay on continuously or not run at all. Circuit Description:The 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...