CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – 019-311   Real-Time Clock Battery Backup Module

The real-time clock battery is connected to the engine harness main branch directly under the 50-pin engine electronic control module (ECM) connector.

The ECM uses the real-time clock feature to time-stamp faults and other data with the time and date. The battery is used to power the real-time clock circuitry in the ECM when vehicle battery power is removed from the ECM. If a battery is installed, the ECM clock will maintain the correct time and date with power removed from the ECM, provided the engine harness connector remains plugged into the ECM.

If a real-time clock battery is not installed on the engine, it will be necessary to set the time and date using INSITE™ electronic service tool whenever the Real-Time Clock feature is enabled in the ECM, and the vehicle battery power is removed from the ECM.

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

Locate the real-time clock battery on the main engine harness. Cut the wire tie securing the module case to the harness.

Clean the area around the battery harness connector.

Disconnect the battery from the engine harness.

Use quick-dry electrical contact cleaner, Part Number 3824510, to clean all dirt and moisture from the battery and harness connector.

Do not apply grease or oil to either the harness connector or battery.

Connect the battery to the engine harness.

Secure the battery to the main engine harness using wire ties.