CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 212

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Overview

ISX – Engine Oil Temperature Sensor 1 Circuit SMALL | MEDIUM | LARGE

ISM – Engine Oil Temperature Sensor 1 Circuit SMALL | MEDIUM | LARGE

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 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 a 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. 100-002 in Section E for a detailed component location view.

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 light immediately when the diagnostic runs and fails.
• A default value for the engine oil temperature reading is used.

Conditions for Clearing the Fault Code

The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM. 019-032 in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

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 of this fault code include:

• Open return circuit in the harness, connectors, or sensor.
• Open signal circuit or shorted to a voltage source.

Refer to Troubleshooting Fault Code t05-212