!!
critical HP
Error Code Blinking = 1 Hz (3 B failure)
Three consecutive boot block failures indicate a serious firmware issue or hardware failure.
? What Causes This
Continuous boot issues likely due to critical system errors.
✓ How to Fix It
System board replacement.
Source: page 84 of the official manual
From the manual
This error code appears in:
HP Elitebook 840 G5 Notebook PC