CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 2412

  Printable Version

Overview

ISX and ISM – Fan Speed Sensor SMALL | MEDIUM | LARGE

Circuit Description

The fan speed sensor is a variable reluctance speed sensor. It consists of a coil of wire and an iron core. The target on the fan hub shaft is a ground flat in the center of the shaft. The electronic control module (ECM) interprets this signal and converts it to a fan speed reading.

Component Location

The fan speed sensor is located in the fan hub assembly. Refer to the OEM troubleshooting and repair manual.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes

The ECM detects that the fan speed signal has been lost.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• The fan will only be in the ON or OFF position.

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.

The fan speed sensor is installed by the original equipment manufacturer (OEM). This fault code is triggered when the fan speed signal is reading 0 when the engine is running. This indicates a failed fan speed sensor or a failure in the OEM wiring harness.

Refer to Troubleshooting Fault Code t05-2412