CAT 3126E Fault Code: 168-01 PID: Flash Code 51 SPN: 168 FMI: 1 Low ECM Battery Power

Posted by PerDiezel Solutions on January 12, 2026

This condition indicates that the battery circuit to the Engine Control Module (ECM) has a low voltage condition 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 engine control is in the ON mode.
•The engine is not cranking.
•The engine is running.
•The ECM has been powered for at least three seconds.

The ECM also detects the following conditions:

•Battery voltage to the ECM is below 9 V for 12 V systems for more than 0.5 seconds.
•Battery voltage to the ECM is below 18 V for a 24 V system for more than 0.5 seconds.

Probable Causes:

1) Aftermarket device preventing battery voltage from getting to ECM
2) Problem with wiring between ECM and battery
3) Low voltage battery or failed charging system
4) Keyswitch issue or wiring from keyswitch to ECM or battery
5) ECM Failure

CAT 3126E Fault Code: 168-00 PID: Flash Code 51 SPN: 168 FMI: 0 Excessive ECM Battery Power

CAT 3126E Fault Code: 70-06 PID: Flash Code 49 SPN: 729 FMI: 6 Inlet Air Heater Short Circuit

CAT 3126E Fault Code: 70-05 PID: Flash Code 49 SPN: 729 FMI: 5 Inlet Air Heater Open Circuit

CAT 3126E Fault Code: 186-14 PID: Flash Code 47 SPN: FMI: PTO Engine Shutdown Switch Occurrence

CAT 3126E Fault Code: 71-14 PID: Flash Code 47 SPN: FMI: PTO Shutdown

CAT 3126E Fault Code: 71-01 PID: Flash Code 47 SPN: FMI: Idle Shutdown Occurrence

WARNING!