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error HP
Error Code Red flashing LED three times then white four times continuously afterward
Power supply fault or overload, possibly due to improperly installed devices.
? What Causes This
Overloaded power supply from attached devices causing system failure.
✓ How to Fix It
1. Remove components one by one until identifying the faulty device and replace it with a known working component.
Source: page 79 of the official manual
From the manual
This error code appears in:
HP Prodesk 400 G3 Desktop Mini PC