!
error HP
Error Code 1 blink every second followed by a 2 second pause
CPU thermal shutdown.
? What Causes This
Overheating.
✓ How to Fix It
Power off the computer, allow it to cool down for several minutes, and then restart.
Source: page 2 of the official manual
From the manual
This error code appears in:
HP Elitedesk 800 G1 Small Form Factor PC