Cummins ISB4.5 CM2150 Fault Code: 1678 PID: 205D SPN: 3031 FMI: 3 Aftertreatment Diesel Exhaust Fluid Tank Temperature Sensor – Voltage Above Normal or Shorted to High Source.

Circuit Description
The aftertreatment diesel exhaust fluid temperature sensor is used to monitor the temperature of the aftertreatment diesel exhaust inside the diesel exhaust fluid tank. The diesel exhaust fluid controller monitors the voltage on the signal pin, converts this to a temperature value, and communicates this value to the engine ECM.

Component Location
The aftertreatment diesel exhaust fluid temperature sensor is located in the diesel exhaust fluid tank. Location of the tank and temperature sensor is OEM dependent. Refer to the OEM service manual for more information.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The ECM detects that the aftertreatment diesel exhaust fluid tank temperature sensor signal voltage is above a calibratible value when the keyswitch is in the ON position.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the MIL immediately after the diagnostic runs and fails.
-Engine torque will be reduced.

Conditions for Clearing the Fault Code
-This fault code can not be cleared with INSITE™ electronic service tool.
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE light and/or MIL immediately after the diagnostic runs and passes.
-Use INSITE™ electronic service tool to verify that the fault code is inactive.
-The inactive fault code will be cleared from memory after 9600 hours of engine operation without a re-occurrence.

Shop Talk
The aftertreatment diesel exhaust fluid temperature sensor shares return wires in the engine harness with other sensors. An open return can cause multiple fault codes to be active.

Possible Causes
-Open return circuit in the harness, connectors, or sensor
-Open signal circuit or shorted to a voltage source.