Strange symptoms, CMOS corrupted?

[HerbertTheGlobe]

Hi guys, I have a problem that I cannot seem to fix.

For the last couple of months, randomly, bluetooth would cease to work on my laptop. All connections would break, however windows 11 settings would show the devices as still being connected -- and while the switch would be in the 'on'-position, it would say off. Then upon pressing the switch, closing settings, and opening them again, all devices and the bluetooth on/off switch would be gone.

In the device manager, the MediaTek bluetooth adapter gave an error code 43, seemingly having crashed. I tried every option under the sun, but the problem wouldn't go away.

In addition, while troubleshooting this issue, I performed a hardware reset. Upon starting, the laptop gave an error that the CMOS checksum was invalid (CMOS reset error 502). However, after letting it do its thing, the laptop would restart as normal, nothing would be fixed, and the next hardware reset the exact same error would return.

And when I checked the BIOS setup options as the error requested, I spotted that in the boot options, the network adapter was shown with an exclamation mark, making me believe these two issues to be connected.

So finally, having tried nearly everything I could find on the internet and having run all of the computer's troubleshooters, I came to the conclusion that I should just try to manually redownload the latest BIOS version, in the hopes that it would fix something...

And then I found no BIOS-downloads for my specific laptop/processor combination on the HP website.

Great.

So I'm burnt-out and all out of ideas, and any help would be lovely 🙂

[Deep_World]

Hi  @HerbertTheGlobe 
 
Welcome to the HP Support Community!

Thank you for reaching out and for providing such a detailed explanation of the issue. I can understand how concerning it is to see multiple symptoms occurring together, especially when Bluetooth functionality, BIOS messages, and hardware components all appear to be affected.

To assist you further, could you kindly confirm the following details:

• Have you noticed whether the Bluetooth issue occurs while gaming, after waking from sleep, or completely at random?
• Does the Wi-Fi connection remain stable when Bluetooth stops working?
• Have you run the HP Hardware Diagnostics UEFI test? If yes, were there any failure IDs reported?
• Are you using the original HP power adapter?

Based on the symptoms you've described, the Bluetooth Code 43 error, the recurring CMOS Checksum Invalid (502) message after a hardware reset, and the network adapter warning in BIOS may indicate either a firmware-related issue, a BIOS configuration issue, or a problem with the wireless module itself.

Meanwhile, you can kindly try the below steps and confirm : 

1. Load BIOS Defaults

1. Shut down the notebook.
2. Press F10 repeatedly at startup to enter BIOS.
3. Select Restore Defaults (or Setup Defaults).
4. Save changes and exit.
5. Restart the computer and monitor the behavior.

2. Perform an hard Reset (Click here for steps )

1. Shut down the notebook.
2. Disconnect all external devices.
3. Connect the AC adapter.
4. Press and hold the Power button for 25 seconds.
5. Release the button and start the notebook normally.

3. Reinstall the MediaTek Bluetooth Driver

1. Open Device Manager.
2. Expand Bluetooth.
3. Right-click the MediaTek Bluetooth device and select Uninstall device.
4. Check Delete the driver software for this device if available.
5. Restart the notebook.
6. Install the latest wireless and Bluetooth drivers from HP Support.

4. Disable Power Management for the Wireless Adapter

1. Open Device Manager.
2. Expand Bluetooth and Network Adapters.
3. Open the properties of the MediaTek adapter.
4. Go to Power Management.
5. Uncheck Allow the computer to turn off this device to save power.
6. Click OK and restart.

Kindly refer to the following HP documents for additional guidance:

• HP Notebook PCs - CMOS Reset (502) Error - click here
• HP PCs - Troubleshooting Bluetooth Connection Issues - click here 
• HP PCs - Updating BIOS - click here 

I hope this helps. 

[HerbertTheGlobe]

Thanks for the reply!

First concerning Bluethooth:

I've reset the laptop to factory settings (as I was planning to do so anyhow), and it hasn't failed since. I'm hopeful that this has at least fixed the more urgent issue, though in case it returns I'll put the requested information here so I don't forget:

• The issue would occur at random, though it seemed to do so more often when multiple devices were connected simultaneously.
• Wi-Fi was not affected.
• The computer was not allowed to turn off the MediaTek Bluetooth Adapter to save power (this was one of the first things I checked).

As for the CMOS issue:

• The UEFI memory test passes, as do all tests run either through HP Hardware Diagnostics or directly from the BIOS.
• I am using the original power adapter.
• I have tried both having BIOS restore the default setup and performing a hard reset before, and doing so again after the factory reset did not show any differences to previous behavior. The hard reset still results in a CMOS Reset (502) error every time.
• I have attempted to go through the process of manually updating the BIOS, however, as previously stated, the HP website does not show any download options for my specific laptop/processor combination.

[Deep_World]

Hi @HerbertTheGlobe 
 

Thanks for your response and Thank you for the update and for confirming the troubleshooting completed. Since the factory reset appears to have stabilized the Bluetooth issue, but the CMOS Reset (502) error still occurs after every hard reset, I want to provide a straightforward assessment.

What this indicates

The most likely causes at this stage is Corrupted BIOS firmware that was not fully corrected by the current BIOS installation or a failing RTC/CMOS circuit on the motherboard.

Since the issue persists even after restoring defaults, performing hard resets, and running diagnostics successfully, kindly try the below steps and confirm : 

Perform a BIOS Recovery (Click here for steps)

1. Turn the notebook off.
2. Press and hold Windows + B.
3. While holding those keys, press and hold the Power button for 2-3 seconds.
4. Release the Power button but continue holding Windows + B until the BIOS Recovery screen appears.
5. Allow the recovery process to complete.

Then Test Again after recovery:

1. Load BIOS defaults.
2. Save and Exit.
3. Perform one hard reset.
4. Check whether the CMOS Reset (502) message returns.

If the 502 Error Still Appears

If the message continues after BIOS recovery, it points away from software and toward a hardware-related issue. In that situation, the notebook should be evaluated by an authorized HP service center.

I hope this helps.