Cummins ISB4.5 CM2150 Fault Code: 1668 PID: 203C SPN: 1761 FMI: 4 Aftertreatment Diesel Exhaust Fluid Tank Level Sensor Circuit – Voltage Below Normal, or Shorted to Low Source.

Circuit Description
The aftertreatment diesel exhaust fluid tank level sensor is used to monitor the aftertreatment diesel exhaust fluid level inside the aftertreatment diesel exhaust fluid tank. The aftertreatment diesel exhaust fluid tanks level sensor is a combination sensor with the aftertreatment diesel exhaust fluid temperature sensor. The level and temperature sensors share a common return circuit.

Component Location
The aftertreatment diesel exhaust fluid tank level sensor is located in the aftertreatment diesel exhaust fluid tank. Location of the tank and level 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 level sensor signal voltage dropped below a calibratible value while the keyswitch was 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.
-Diesel exhaust fluid injection into the aftertreatment system is disabled.
-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 lamp and/or MIL immediately after the diagnostic runs and passes.
-Use INSITE™ electronic service tool to verify the fault code is inactive.
-The inactive fault code will be cleared from the memory after 9600 hours of engine operation without a reoccurrence.

Shop Talk
The aftertreatment diesel exhaust fluid tank level sensor shares supply and return wires in the engine harness with other sensors. Opens and shorts in the engine harness can cause multiple fault codes to be active.

Before troubleshooting Fault Code 1668 (Aireless), check for multiple faults.

Possible Causes
-Signal circuit open or shorted to ground in the engine harness or sensor
-Supply line open or shorted to ground.