CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 441

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Overview

ISX and ISM – Unswitched Battery Supply SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. There is one 30-ampere fuse in the unswitched battery wires to protect the original equipment manufacturer (OEM) harness. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned on. The battery return wires are connected directly to the negative (-) battery post.

Component Location

The ECM is located on the intake side of the engine. The ECM is connected to the battery by the OEM harness. This direct link provides a constant power supply for the ECM. Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed component location view. The location of the battery will vary with the OEM. Refer to the OEM troubleshooting and repair manual for battery 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 main battery supply voltage is less than +6-VDC.

Action Taken When the Fault Code is Active

• The ECM logs the fault code immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code

The ECM will turn off the fault code immediately after the battery voltage is above +6-VDC.

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.

This fault code is logged when the ECM battery supply voltage drops below +6-VDC.

• Verify that the ECM unswitched power supply is coming from the batteries and not the starter or other device. Check for possible weak batteries.
• If the ECM unswitched battery supply is taken from the starter, check for low voltage during cranking. Low voltage during cranking can cause the ECM power supply to drop below specifications and log Fault Code 441.

Refer to Troubleshooting Fault Code t05-441