901 Chassis fan error at boot only when riser installed

[sidb-1]

When the PCIe riser is installed, I get a POST error '901-Chassis Fan Not Detected (rear)' . The computer waits for the user to press enter then boots normally. Without a riser in the machine it boots without a problem.  I have updated to the latest bios, removed and replaced the fan (it is running). The processor fan also works.

Thanks in advance for any help!

[Bill_To]

Greetings @sidb-1 

Welcome to the HP Forum. 

I'm trying to link the use of a PCIe riser card to a fan sensor problem.

I've got nothing. 🤔  ??

What is the PCIe card's function? Storage, Ethernet, WIFI, or video capture?

When this card is installed do you see any problems or conflicts in: Device Manager or System Information>System Summary>Hardware Resources?

Although the 901 startup error is a HP BIOS thing, the BIOS may also be mis-reporting the installed device to Windows.

A BIOS update should reset the BIOS to defaults. But have you also tried resetting CMOS when the riser card is installed in the PCIe slot?

Do you need the PCIe add-in component?

If yes, you may have to live with the 901 error at startup.

Regards

[sidb-1]

Thanks for the suggestion however no change. The riser card is a standard HP one with no cards in it and the error occurs at POST. The fan works, even when the riser is installed so may have to live with it or reallocate that machine to a task not requiring the cards!

[sidb-1]

Thank you to a very efficient HP support guy for coming so quickly. The verdict is that the BIOS error is misleading - the problem is with the riser fan instead of rear it . There isn't one!