Elitebook 850 G5 BIOS bricked

[achim6]

I have an Elitebook 850 G5 which was bricked by a BIOS update. When turning on the laptop, the power and wifi front lights turn on and the fan starts spinning, but I don't get any image on the internal display or an external screen.  The support document at https://support.hp.com/us-en/document/ish_3932413-2337994-16 suggests that there is an "Automatic BIOS recovery" which - if I understand this correctly - is simply using a previous version from a hidden partition on the SSD. The laptop currently doesn't have a SSD anymore. I could insert a blank one or prepare one with an ISO image or something like that if it would help. Or is there another way?

[TzortzisG]

Hello achim6.

Bricked laptops due to incidents during the BIOS upgrade are almost impossible to "fix" on modern or semi-modern systems. Anyways, I consider this as the mother-document since it contains links to the one you found and also this second relevant one: 500, 501, or 502 error. The procedure you're looking for is at the bottom of both pages, using a USB flash drive. It can't hurt to try this, but as mentioned above chances are very very (very) slim to none. If this fails, externally flashing the BIOS chip with a "good" firmware is the only method known to salvage a notebook in this state....

[achim6]

Well, thanks for trying to help. I tried the USB stick, but it didn't work.

[TzortzisG]

Yes, there's no point to trying these methods on anything past a G1 Business laptop.

The UEFI firmware code is too complicated on newer systems, so when a BIOS update goes wrong the code is completely corrupted and you might as well have a new completely clean BIOS chip on the motherboard. For these methods to work, you need a small fraction of the code (the first lines) to still be OK. Anyways, I have discussed this some years ago on a previous thread: https://h30434.www3.hp.com/t5/Business-Notebooks/Caps-Lock-and-Num-Lock-Blinking-5-Times/td-p/871318.... You can still save this system by externally flashing the chip, many stores do this nowadays, as you can imagine this is a very lucrative business (with the whole Windows Update pushing BIOS upgrades on the sly thing).

[Nemesis952]

I have found 2 temporary workarounds for this.

When the keyboard lights up and fan runs but no display, hold down the power key until it switches off. Wait a couple of seconds and switch on. It should start up after a couple of seconds. It may be necessary to do it a couple of times to get a normal startup.

If that doesn't work, pull of the bottom cover, disconnect the the main battery cable and the RTC coin battery cable. Leave for at least 30 minutes to clear settings. Connect cables and start normally.

I've had to do step 2 when it decides the NVME doesn't exist, but then I've left the batteries disconnected overnight just to be sure.

This doesn't remove the need to backdate the BIOS but should help you get into the OS to do the downgrade.