This is most likely a corrupted/damaged BIOS. I have had this happen to one of the machines at the office where I work, processed a BIOS update that botched and would only flash white, no pattern.
I had to make a BIOS recovery flash drive. You can find the downloader for the BIOS update for that at HP's support site for your model (The Elitebook 840 G2 drivers and downloads site is here). If you run the installer on a different Windows machine, it should give you the option to create a recovery drive for another device. I often get an error with these where it cannot save to the required folder because it doesn't exist or something to that effect. You just need to create that folder in the root directory on the flash drive.
Once the recovery drive is created, plug it into the device that needs recovery and then power it on. Theoretically it should recognize the BIOS update file and process the update.
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Here is HP's codes and solutions:
https://support.hp.com/nz-en/document/c0...
What light pattern or beeps with just the battery?
crwdns2934271:0crwdnd2934271:0 mike crwdne2934271:0
@aactech Thanks, but as I stated before, there is no pattern. I looked at those before posting my question and I couldn't find anything that helped. When the computer is plugged in, the lights come on and flash quickly and evenly with no pattern or changes. There are no short flashes, or pauses at all.
crwdns2934271:0crwdnd2934271:0 Mike Stettler crwdne2934271:0
The computer was knocked off a table while plugged in. originally it was thought that the power adapter was damaged, but I can trace voltage through the adaptor on the motherboard. It also ran off battery power afterwards without a problem until the battery died.
crwdns2934271:0crwdnd2934271:0 Mike Stettler crwdne2934271:0
Did u got the solution , if yes please share with me i h same problem
crwdns2934271:0crwdnd2934271:0 Hashim crwdne2934271:0
i kept reseating the ram and the battery which caused the laptop not to boot and it kept the power to blink
crwdns2934271:0crwdnd2934271:0 Abdullah Ahmad crwdne2934271:0