Cummins ISB4.5 CM2150 Fault Code: 1689 PID: SPN: 251 FMI: 2 Real Time Clock Power Interrupt – Data Erratic, Intermittent, or Incorrect.

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, 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.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The real-time clock in the ECM lost power.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE light on the second ignition cycle when the diagnostic runs and fails.

Conditions for Clearing the Fault Code
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE light and the fault code will go inactive immediately after the diagnostic runs and passes.
-This fault code can also be cleared with INSITE™ electronic service tool.

Shop Talk
Possible causes for this fault are weak or damaged real-time clock battery, damaged 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.