HP 90B error after starting up desktop (fan goes really high)

[Delta280]

Hello, recently I have been getting the CPU Fan (90B) error on my HP Envy 750-427c.  I have done lots of investigating for this, and I'm not sure if it's a motherboard relating problem or a fan related problem.

I have been getting this error occasionally in the year 2020 (about 4 times overall), but I did notice my cpu fan heatsink would have a delayed start by about 5 seconds, and then it would rev up to a very fast speed, being loud and then revving down.  Eventually, however, it would delay so much to the point that this error message would pop up, and it would even be louder than before.  This scenario is shown in the video attached.

What is interesting though, is that if I press enter to get past the error message, the fan works fine.  In fact, I played about 5 hours of Assassin's Creed Odyssey and there were no issues with temps.  This is why I'm not sure if its a CPU fan issue, or something is wrong with the BIOS or even the motherboard.

I dusted the system which solved nothing, and I reinstalled the latest BIOS update which didn't have any affect either.  Is this because the BIOS is an older version and is not supported anymore?  Or is the CPU fan faulty, in which I should order another one?  Or is the motherboard faulty?  Everything else on the system works fine.  By the way, I should mention that I did upgrade the prebuilt's GPU, PSU, and added another hard drive.  Those parts are all working fine, but this fan is causing problems.  What should I do?

[itsmyname]

Upon power-on, some motherboards do run the fan at 100% speed (and 100% noise) for a few seconds, until the motherboard can measure the temperature of the motherboard and of the CPU.  When the motherboard detects that the motherboard/CPU are operating at "normal" temperatures, the motherboard tells the variable-speed fan to slow down, which causes it to make less noise.

In your case, either the fan is not responding to the "spin slower" command, and it keeps "roaring", or the motherboard is not sending the "spin slower" command to the fan.   

If the fan does go quiet, after a few seconds, you do not have to do anything.

If the fan still runs at 100%, it is less expensive to replace the fan than it would be to replace the motherboard and the fan.