CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 195 (2-Wire Sensor)

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Overview

ISX and ISM – Engine Coolant Level Sensor 1 Circuit SMALL | MEDIUM | LARGE

Circuit Description

The coolant level sensor is a switch and is used to measure the level of the engine coolant in the radiator top tank. The coolant level sensor is immersed in the coolant and returns a different signal voltage when immersed in coolant versus being out of coolant. The electronic control module (ECM) supplies 5 volts to the coolant level signal circuit. The resistance of the engine coolant level sensor changes based on the coolant level. The sensor resistance is between 5.4k ohms and 34k ohms when the sensor is submersed in coolant. The sensor resistance is between 333k ohms and 880k ohms when the sensor is not sumbersed in coolant. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the level of the engine coolant.

Component Location

The engine coolant level sensor is typically located in the radiator top tank or surge tank. Refer to the OEM troubleshooting and repair manual for location.

Conditions for Running the Diagnostics

This diagnostic runs continously when the keyswitch is in the ON position, or when the engine is running.

Conditions for Setting the Fault Codes

The ECM detects that the coolant level signal voltage is greater than 5.124-VDC for more than 20 seconds.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• No engine protection will be available for low coolant level.

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. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

Possible causes of this fault code include:

• Open return or signal circuit in the harness, connectors, or sensor.
• Signal wire shorted to sensor supply or battery voltage.

Refer to Troubleshooting Fault Code t05-195