Cummins ISB4.5 CM2150 Fault Code: 212 PID: 175 SPN: 175 FMI: 3 Engine Oil Temperature Sensor 1 Circuit – Voltage Above Normal or Shorted to High Source.

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 electronic 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 low, 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 high, 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 signal voltage is greater than 5.13-VDC for more than 1 second.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
-A default value for the engine oil temperature reading is used.

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 the 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.
-For On-Board Diagnostics (OBD) engines, the ECM will turn off the MIL after three consecutive trips where the diagnostic runs and passes.
-The “Reset All Faults” command in the INSITE™ electronic service tool can be used to clear active and inactive fault codes, as well as extinguish the MIL for OBD engines.

Shop Talk
The engine oil 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.