CPU Fan Error 90B - Pavilion Desktop

[ar_Touchsmart]

Hello, my Pavilion Desktop is repeatedly giving me a "90B" error message upon startup and then turning off, as described on the following support page:

https://support.hp.com/us-en/document/c03620929

I have attempted the fixes on the above page, without solving the problem. Sometimes it will startup without this error, but usually I get this error message. I've started the computer with the cover off so that I can see the fans; when this error occurs, the CPU fan stays still for about 3 seconds after turning on the system, then runs at high speed for about 1 second, then settles into a steady pace until the computer turns off. 

I would appreciate any suggestions for how to fix this -- my computer is not under warranty (it's 3-4 years old). Additional details are below:

1. After this error message started, I cleaned the internal components with an air duster.

2. One one of the few times that it started properly, I updated the BIOS. This is actually the last time I was able to start it without obtaining the message. (I've tried 5-10 times since them)

3. I then attempted a 'hard restart' by unplugging the computer and holding the power button to drain any remaining charge.

4. My room is fairly cool (70 F)

5. The computer is HP Pavilion Desktop 570-p017c.

6. The error message starts with "A fan is not operating correctly". Then it provides the option to boot the system, but warns against doing so. Then it says "CPU FAN (90B)". Then finishes by directing me to the hp website "www.hpt.com/techcenter/startup", which is where I found the above troubleshooting article. The last line on that article is "If the error message still persists, contact HP."

Any thoughts would be appreciated. Do I need to replace the fan? Is that even possible?