CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 319

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Overview

ISX and ISM – Real-Time Clock Power Circuit SMALL | MEDIUM | LARGE

Circuit Description

Under ordinary operating conditions, the real-time clock in the electronic control module (ECM) is powered by the vehicle’s batteries. If battery power to the ECM is lost, then the real-time clock will be powered by a battery in the engine harness (if equipped).

Component Location

The real-time clock battery is secured to the engine harness near the ECM. Refer to Procedure 100-002 (Engine Diagrams) 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 real time clock battery voltage is 3.3 VDC.

Action Taken When the Fault Code is Active

• The ECM flashes the amber CHECK ENGINE light at initial key-on when the diagnostic runs and fails.
• The real time clock values in the ECM data will be incorrect.

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.

This fault indicates that the real-time clock in the ECM lost power. Possible causes for this fault are weak or failed real-time clock battery, failed wiring or connectors between the battery and ECM, or the engine is not equipped with a real-time clock battery and the vehicle battery power to the ECM is lost.

Refer to Troubleshooting Fault Code t05-319