Cummins ISX15 CM2250 (2010-12) Fault Code: 1668 (2 Wire) 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 tank 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.

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

Conditions for Setting the Fault Codes
The diesel exhaust fluid controller detects that the diesel exhaust fluid tank level signal voltage is less than 0.25-VDC for more than 1 second.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.
Conditions for Clearing the Fault Code
To validate the repair, start the engine and let it idle for 1 minute.
The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
The ?Reset All Faults? command in INSITE? electronic service tool can be used to clear active and inactive faults.

Shop Talk
Possible causes of this fault code include:

Signal circuit open or shorted to ground in the engine harness or sensor
Supply line open or shorted to ground.
The type of diesel exhaust fluid tank temperature and level sensor used can vary depending on the vehicle OEM. As a result, the physical and/or electrical sensor configuration may vary slightly from what is shown in the troubleshooting and wiring diagram information.

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Cause:
1) Aftertreatment DEF controller harness
2) ECM calibration