CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 197

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Overview

ISX and ISM – Engine Coolant Level 2-Wire Sensor Circuit SMALL | MEDIUM | LARGE

ISX and ISM – Engine Coolant Level 3-Wire Sensor 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 submersed 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 serive manual for the location.

Conditions for Running the Diagnostics

This diagnostic runs continuously 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 is below the normal operating limits.

Action Taken When the Fault Code is Active

• The ECM illuminated the amber CHECK ENGINE light after 20 seconds when low engine coolant level has been detected.

Conditions for Clearing the Fault Code

The ECM will turn off the amber CHECK ENGINE light immediately after 20 seconds of detecting the correct engine coolant level.

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, calibrate the ECM. Refer to Procedure 019-032 in Section 19.

This fault code goes active when the coolant level inside the radiator top tank or surge tank drops below the sensor level. Fill the top tank with coolant.

Refer to Troubleshooting Fault Code t05-197