CAT 3406E (Prefix 1MM or 2WS) Fault Code: 21 PID: SPN: 232 FMI: 4 5 Volt Supply voltage low
The Engine Control Module (ECM) detects the following conditions:
•The 5 volt supply is less than 4.84 VDC for more than one second.
•The ECM has been powered for at least three seconds.
Sensors that are regulated with 5V: Boot pressure, atmosphere pressure, engine oil pressure, coolant temperature, intake manifold air temperature, fuel temperature
Probable Causes:
1) ECM Connection/Harness
2) Sensor Failure
3) Sensor wiring failure
4) ECM Failure
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