!!
critical HP

Error Code Red LED 4 blinks every second followed by a 2 second pause

The system is experiencing power failure, commonly due to an overloaded power supply or bad connection.

? What Causes This

Power supply overload, loose connections or failure of the power supply unit (PSU).

How to Fix It

  1. Inspect and tighten any loose power cables and connectors.
  2. Replace faulty components such as PSU if necessary.
  3. Contact support for further assistance with unstable conditions.

Source: page 4 of the official manual

From the manual

Manual page 4 — HP error Red LED 4 blinks every second followed by a 2 second pause

This error code appears in:

HP Elitedesk 800 G1 Small Form Factor PC