Cummins ISB4.5 CM2150 Fault Code: 3492 PID: SPN: 251 FMI: 10 Real Time Clock – Abnormal Rate of Change.

Circuit Description
The real-time clock consists of a timing chip internal to the engine control module (ECM) which monitors engine off time, i.e. how long the engine has been shut down.

Component Location
The real time clock is a timing chip internal to the ECM and can not be serviced separately.

Conditions for Running the Diagnostics
This diagnostic runs after initial key-on and takes approximately 15 minutes to complete.

Conditions for Setting the Fault Codes
The engine off timer is not counting correctly and does not match other timers in the ECM.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
-The ECM will not be able to monitor engine off time accurately.

Conditions for Clearing the Fault Code
-To validate the repair, key-off for 1 minute, then key-on for 15 minutes.
-The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
-The ECM will turn off the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with the INSITE™ electronic service tool.

Shop Talk
Monitoring the engine off time is necessary in order to make sure that all other engine sensors and actuators are performing correctly. If the ECM is recalibrated or replaced during the repair and the fault code is no longer present, the instructions in the “Conditions for Clearing” section must be followed in order for the diagnostic to run again and validate the repair.

Potential causes of this fault code include:
-Failed real time clock chip internal to the ECM
-Engine calibration issue