I've got a Thinkpad T440P which is an 10yrs. old model, I used Linux Mint Debian with it. The Bluetooth suddenly failed my earbuds give no sound although it said connected, so I check the system settings and the Bluetooth windows show nothing and does not respond, and the Bluetooth applet on taskbar disappeared, so I reboot. During reboot I saw lot of error message pops up said unable to stop the Bluetooth, I force a reboot anyway but the Bluetooth still not working. Then I do a h/w check, I removed the wireless module, spray contact cleaner to it and put back. I find the module is exceptional small, and the antenna plug is so tiny very hard to handle, I got other module for notebook but too big to put it, so that I still need to use the original one. I noticed that there are 2 spare wires, one with heat shrink tube cover I believe is the temperature sensor for the SSD, the other is for antenna, but what is it for, cellular ? after I clean the contact the Bluetooth works again.

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From this site: https://support.lenovo.com/ca/en/sol...thinkpad-t440p

I see this in Networking:

Notice the wireless WAN; that's my guess. Possibly look at the P/N of the card, and you can find more detailed information.

Thanks I will take a look