Cummins X12 CM2350 X119B (2018 & Newer) Fault Code: 3243 PID: SPN: 3060 FMI: 18 Engine Cooling System Monitor- Data valid But Below Normal Operating Range- Moderately Severe Level

Circuit Description
The coolant temperature sensor is a variable resistor sensor and is used to measure the temperature of the coolant of the engine. The engine control module (ECM) supplies 5 volts to the coolant temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the coolant temperature.

Component Location
The engine coolant temperature sensor is located on the thermostat housing.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the engine is running if the coolant temperature was less than 52°C [126°F] when the engine was started.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the engine coolant temperature did not reach 72°C [162°F] in a specified amount of time.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL) after the diagnostic fails on two consecutive trips.

Conditions for Clearing the Fault Code
To validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop and go city type driving and steady state highway type driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.
To validate the repair using a Chassis Dynamometer, utilize a routine that incorporates acceleration and motoring events, steady state highway type operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.
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 immediately after the diagnostic runs and passes.
For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk
Possible causes of this fault code include:

Low coolant level, or air in the cooling system
Malfunctioning coolant temperature sensor
Malfunctioning engine coolant thermostat.

Possible Cause:
1) Thermostat failure
2) ECM calibration