Cummins ISX15 CM2250 (2010-12) Fault Code: 421 PID: SPN: 175 FMI: 16 Engine Oil Temperature- Data Valid But Above Normal Operating Range- Moderately Severe Level

Circuit Description
The engine oil temperature sensor is a variable resistor sensor and is used to measure the temperature of the engine oil in the oil rifle. The engine control module (ECM) supplies 5 volts to the engine oil temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the engine oil temperature. When the oil temperature is cold, the sensor or thermistor resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to a ground. Therefore, the ECM senses a high signal voltage or low temperature. When the oil temperature is warm, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the ECM senses a low signal voltage or high temperature. The engine oil temperature sensor is used to monitor the engine oil temperature. If the temperature exceeds a calibration limit, an engine protection fault code will be triggered.

Component Location
The engine oil temperature sensor is located in the oil rifle.

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 engine oil temperature is greater than the warning engine protection limit for 5 seconds.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
The torque output of the engine will be reduced.
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 driving and steady state highway 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 Test, utilize a routine that incorporates acceleration and motoring events, steady state highway 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 oil temperature decreases below the engine protection limit and 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
This fault code indicates that the engine oil temperature has exceeded the warning engine protection limit for oil temperature. Troubleshoot the cause of high engine oil temperature.

Possible Cause:
1) ECM calibration