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Reason:VGT Actuator Driver Circuit (Motor) – 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...

Reason:Sensor Supply 3 Circuit – Voltage Above Normal or Shorted to High Source. High voltage detected on the 5 volt sensor supply circuit to the engine speed sensor. Effect:Engine may run rough, may stop running, may not start, or may be difficult to start. Circuit Description:The sensor supply 3 circuit provides a 5 volt supply to the primary engine speed/position sensor. Component Location:Sensor Supply 3 originates in the engine wiring harness. It provides 5 VDC to the engine crankshaft speed/position sensor. Conditions for Running the Diagnostics:This diagnostic runs continuously when the keyswitch is in the ON position or when the...

Reason:Wheel-Based Vehicle Speed – Data Erratic, Intermittent, or Incorrect. The ECM lost the vehicle speed signal or is reading an erratic value. Effect:Engine speed limited to Maximum Engine Speed without VSS parameter value. Cruise Control, Gear-Down Protection, and Road Speed Governor will not work. Circuit Description:The vehicle speed sensor senses the speed of the tailshaft gear on the vehicle’s transmission. This speed signal is then transmitted to the engine control module (ECM) and converted into a vehicle speed. Component Location:The vehicle speed sensor is located in the rear of the vehicle transmission. Refer to the OEM service manual for location....

Reason:Coolant Level – Data Valid But Below Normal Operational Range – Least Severe Level. Low engine coolant level detected. Effect:None on performance Circuit Description:The coolant level sensor is a switch and is used to measure the level of the engine coolant in the radiator top tank. The coolant level sensor is immersed in the coolant and returns a different signal voltage when immersed in coolant versus being out of coolant. The engine control module (ECM) monitors the change in the signal voltage to determine the level of the engine coolant. Component Location:The engine coolant level sensor is typically located in...

Reason:Coolant Level – Data Valid But Below Normal Operational Range – Least Severe Level. Low engine coolant level detected. Effect:None on performance Circuit Description:The coolant level sensor is a switch and is used to measure the level of the engine coolant in the radiator top tank. The coolant level sensor is immersed in the coolant and returns a different signal voltage when immersed in coolant versus being out of coolant. The engine control module (ECM) monitors the change in the signal voltage to determine the level of the engine coolant. Component Location:The engine coolant level sensor is typically located in...