!
error HP
Error Code 3 blinks, 1 blink every second followed by a 2 second pause
Processor is not installed.
? What Causes This
Failed to detect CPU.
✓ How to Fix It
Check the processor socket and ensure the CPU is properly seated. If issues persist, contact support.
Source: page 2 of the official manual
From the manual
This error code appears in:
HP Elitedesk 800 G1 Small Form Factor PC