!!
critical HP
Error Code 4 blinks, 1 blink every second followed by a 2 second pause
Power failure (power supply overload).
? What Causes This
High load or faulty power supply.
✓ How to Fix It
Check the load and connections related to the PSU. If necessary, replace the power supply.
Source: page 2 of the official manual
From the manual
This error code appears in:
HP Elitedesk 800 G1 Small Form Factor PC