!!
critical HP
Error Code 6 blinks, 1 blink every second followed by a 2 second pause
Pre-video graphics error.
? What Causes This
Faulty video card or incorrect configuration.
✓ How to Fix It
Check the installation and connections of any installed discrete GPUs. Replace faulty cards if necessary.
Source: page 2 of the official manual
From the manual
This error code appears in:
HP Elitedesk 800 G1 Small Form Factor PC