CAT 3406E (Prefix 1MM or 2WS) Fault Code: 21 PID: SPN: 232 FMI: 3 5 Volt Supply voltage high
The Engine Control Module (ECM) detects the following conditions:
•The 5 volt supply is greater than 5.16 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
![download Hitachi Construction Machinery MPDr Ver 3.7.0.0 [10.2020] Diagnostic Software](https://www.ecuforcetruck.com/wp-content/uploads/2023/05/MPDR-3.7.00-300x300.png)
