CAT 3406E (Prefix 1MM or 2WS) Fault Code: 51 PID: SPN: 168 FMI: 2 ECM Battery Power Intermittent

Posted by PerDiezel Solutions on January 13, 2026

This condition indicates that the battery circuit to the Engine Control Module (ECM) has a battery condition that is intermittent while the engine is running. If battery voltage disappears without returning, the ECM will not log this diagnostic code and the engine will shut down.

The ECM detects the following conditions:

•The ignition key switch is in the ON position.
•The engine is running.
•The engine is not cranking.
•The ECM has been powered for at least three seconds.

The ECM will detect one of the following conditions:

•The battery voltage drops below 6 VDC for at least 0.50 seconds.
•Three voltage readings in the past seven seconds were below 6 VDC.

Probable Causes:

1) ECM Connection/harness
2) Battery voltage at ECM
3) Truck battery or battery cable issue
4) Aftermarket engine protection switch
5) ECM Failure

CAT 3406E (Prefix 1MM or 2WS) Fault Code: 47 PID: SPN: 71 FMI: 14 PTO Shutdown

CAT 3406E (Prefix 1MM or 2WS) Fault Code: 47 PID: SPN: 71 FMI: 1 Idle Shutdown

CAT 3406E (Prefix 1MM or 2WS) Fault Code: 46 PID: SPN: 100 FMI: 11 Very Low Oil Pressure

CAT 3406E (Prefix 1MM or 2WS) Fault Code: 46 PID: SPN: 100 FMI: 1 Low Oil Pressure Warning

CAT 3406E (Prefix 1MM or 2WS) Fault Code: 42 PID: SPN: 22 FMI: 13 Engine Speed Signal Calibration Not Performed

CAT 3406E (Prefix 1MM or 2WS) Fault Code: 42 PID: SPN: 22 FMI: 11 Primary to Secondary Engine Speed Signal Calibration

WARNING!