16-inch MacBook Pro Bluetooth issue

Here is a summary of the whole thread:

TL;DR:

• It's apparently possible to unfix the problem with a BT 2.0 dongle
• For those that are scared to break it again (after logic board replacement OR BT 2.0 fix), they can run a NVRAM command to never switch BT controllers again (need to re-run after NVRAM reset):

sudo nvram bluetoothHostControllerSwitchBehavior="never"

Might be best to put that in a startup script and only change if needed.

• It seems to have to do with Power Management and seemingly a EFI firmware bug introduced in Catalina as it's not possible to break Mojave in the same way.

So in summary it's several factors that came together here to create this bug:

• a) A likely firmware bug in the EFI in Catalina.
• b) A pretty unsafe default for switching Bluetooth controllers - which most users likely don't want anyway.
• c) Maybe: A CSR USB controller using the exact same chip as the internal one. (if I am able to unbreak my device, I will try to re-break with a Broadcom 4.0 device, too)

Long version:

I have been bitten by the Bluetooth bug, too that breaks the internal Bluetooth module on Mac Book Pro 16inch if you accidentally plug in an USB CSR 4.0 Bluetooth dongle.

• It seems to not happen on Mojave - so it's also related to a driver bug in Catalina regarding power management.
• It happens in the first place because the nvram default behavior is to switch over to external Bluetooth by default.

The symptom is:

• The Bluetooth chip gets too little power and hence fails to connect to devices and if it does connection is spotty. While on MacBook Pro 16inch it completely fails, other Macs can have bad Bluetooth behavior that is "spotty".

• The solution of AppleRepair so far has been to completely replace the logic board, which fixes it till the next Dongle is plugged in and obviously is quite costly for a pure software bug.

Several observations:

• The current theory is that the internal firmware mixes up the external CSR chip for it's own and saves the power requirement of the external chip (which is less as its powered by BT) and then uses this for the internal chip.

• a) It is highly debatable to make the switch over to external dongle the default for all users if the functionality is usually only wanted by a handful of developers that develop Bluetooth LE applications. In fact it also breaks it for iOS developers and everyone that wants to use a Dongle to use with a VM:

• https://developer.apple.com/library/archive/technotes/tn2295/_index.html#//apple_ref/doc/uid/DTS40012211-CH1-UNDERSTAND_SWITCH__BEHAVIOR

• Fortunately that is easily remedied with a nvram command to change the behavior. It would be great if Apple changed this in the next minor Catalina release by default to not switch over to external Bluetooth automatically, but make it an option to select the Controller (like you can do with Bluetooth Explorer). The setting could be stored and automatically be applied after every reboot to what the user configured. That would prevent the bug in probably most user cases until a proper fix can be found.

• b) It is unclear if a pure software fix could fix this as per the reports the issue remains once it has happened even if you boot into Windows / Bootcamp. However it is seemingly possible (per the above accepted answer) to unfix that issue with an older CSR Bluetooth 2.0 dongle. This probably helps, because it has a different power requirement as it predates Bluetooth LE and hence the MacBook FW gives the internal Bluetooth chip more power again.

• c) Someone tried to port the Bluetooth drivers from Catalina to Mojave and it did not work.This points to the fact that it likely is an EFI / soft FW update that broke this in Catalina and not a pure software bug.

Overall it seems Apple would have several ways to fix / work around this:

• Fix the EFI to fix the PM bug. (that gives hope that it can be fixed 100% and also restored affected devices without logic board replacement)
• If that fix takes a while to do, at least change the default and put out a changelog for those few that need to use an external Bluetooth dongle to replace the internal one.
• Create a program that does whatever the diagnostics on the Apple Wifi in the repair shop does to reset the firmware to sane values.
• Create a device to emulate the USB behavior of a 2.0 Bluetooth device to fix broken devices [unlikely as that is].

In theory VirtualHere + ZeroTier could be used to share a BT 2.0 dongle from one machine on the internet to another one and unbreak something remotely. (not sure if that would work in practice though as emulation is not perfect. Though I know that Bluetooth over Internet works well as that is ironically how I broke my BT in the first place as I needed a dongle for bluetooth-over-internet)

jamiefromkirkcaldy wrote:

I had done a full reinstall by nuking the T2 Firmware and it hadn't solved it on mine.

A 2019 iMac does not have an Apple T2 Controller. See About the Apple T2 Security Chip - Apple Support and iMac (Retina 5K, 27-inch, 2019) - Technical Specifications for reference.

I wonder if I do a few complete installs if it might work?

It is worth an experiment. The power issues on the 16-in MBP are unrelated to the 2019 iMac experiment. Posts in this discussion have tried to erase/re-install macOS on the 16-in MBP, but without positive results.

OK,

target mac's bluetooth was rendered unusable by some bt 4.0 dongle and I used other older bt 2.0 dongle to troubleshoot and eventually to get it working again.

To replicate successful recovery just yesterday that I did:

1. Cleared SMC, NVRAM
2. reset bluetooth from shift+option icon debug method
3. installed blueutil, with brew installed from terminal brew install blueutil
4. plugged in the bluetooth dongle and fiddled around it until bluetooth works with with the dongle (bluetooth explorer app, turning bluetooth on and off again multiple times)
5. connected to android phone using the bluetooth dongle (paired etc, also I had visible connectivity light on the dongle that I noticed to be blicking time to time)
6. removed the bluetooth dongle -> paired android device disappears from the bt device list
7. restarted to recovery
8. mounted macos partition in recovery
9. openned terminal in recovery
10. executed cd /PATH/TO/MOUNTED/MACOS/VOLUME + /usr/local/Cellar/blueutil/2.6.0/bin/blueutil
11. executed blueutil -p 0
12. executed blueutil -p 1
13. executed blueutil --inquiry
14. blueutil did not return anything even if android device was discoverable
15. rebooted to macos -> bluetooth still not working
16. shutdown the mac
17. plugged in the bluetooth dongle and turned on the mac and started macos
18. at this point discovering new bluetooth devices used the onboard bluetooth as dongle was not blinking
19. initiated pairing to android but cancelled it from the macos
20. removed bluetooth dongle
21. initiated pairing to android and completed it
22. restarted macos and internal bluetooth was still working

half of things in the list are probably not related why it started working again but this is how I did it.

I am still amazed how such things are even a thing on this expensive machine.

Hi,

I changed the procedure a bit as NVRAM reset was pain to do as I have firmware password set.

Doing SMC reset instead.

https://www.youtube.com/watch?v=2elFJmqJJtI

---

1. For demo purposes I have already broken my internal BT with CSR 4.0 BT dongle

2. Disconnect CSR 4.0 BT dongle if it is still connected

3. option+shift+bt icon - debug - reset the bluetooth module

4. Run “sudo rm /Library/Preferences/com.apple.Bluetooth.plist”

5. Shutdown your Mac and do SMC reset

1. My procedure is following as I have filevault enabled

1. Start your Mac

2. Wait until filevault login appears

3. Press option+cmd+RIGHT SHIFT for 7 seconds

4. While keep holding keys in step 3. also press power button for 7 seconds

1. Fans should briefly spin up and Mac shut power off, keep holding power button for whole 7 seconds

5. If fans did not spin up try SMC reset again

6. Start your Mac to macOS normally without connecting any dongles

7. See Ya soon…

8. After SMC reset

9. Insert BT 2.0 USB dongle

10. Initiate pairing but cancel it from macOS

11. Remove BT 2.0 USB dongle and immediately after try pairing again

12. Failed

13. Trying again

14. Connect your BT 2.0 USB dongle

15. Initiate pairing but cancel it from macOS

16. Cancel pairing then remove BT 2.0 and try pairing again

17. Failed

18. Do step 5. again

19. Check if internal bluetooth is working already

20. Internal BT works again if it does not try steps 9-11 again

21. Done

I just spent the past 2 hours trying all possible combinations of the steps you described to no avail.

macOS just won't recognise the internal module as a HCI Controller anymore.

Using the dongle is the only way to get partial/unstable Bluetooth.

With the Bluetooth Explorer I can see that macOS will pick some BLE devices nearby without a dongle but won't successfully connect to any of them.

Hi,

So I borrowed my friends CSR 4.0 BT USB dongle...

My Mac is following version:

Internal bluetooth is as follows:

...and spent 5 hours with it...

I was able to break my internal BT 5 times and recover 5 times :) but it was well very frustrating...

Following did the trick:

and sorry the list is still long :(

1. option+shift+bt icon -> debug -> reset the bluetooth module
2. sudo su
3. rm /Library/Preferences/com.apple.Bluetooth.plist
4. reboot (to filevault login screen)
5. NVRAM reset (I am not sure but I think the fans must spin up for half a second to the NVRAM reset to be successful, I missed timing many times and it seemed like a normal hard shutdown what happens when you hold down power button for long enough)
6. boot up to macOS normally WITHOUT BT CSR 4.0 connected
7. Trying to recover with CSR 4.0 didn't work even once (I tried 4 of 5 hours to get it to work as this is what most people will have available)
8. I connected my BT 2.0 USB dongle
9. scanned for my android device
10. Initiated pairing for android but cancelled it from macOS
11. removed the BT 2.0 USB dongle
12. immediately after connected to my android device and finished pairing with it
13. BT restored

One time I had to try steps 8 - 12 again

Once I had to do whole 1 - 12 again.

3 times I got it work exactly as listed

There was so much luck involved finding this...

Thanks so much for this. It's got mine working again, but not without some drama.

I ordered the previously linked dongle from ebay and put it in. It got so hot it melted and burned. I'm going to put this down to more bad luck. I then found a 2.1 dongle in stock nearby and went and grabbed it. It's done the trick.

There is one caveat thus far, which is that my Logitech Craft keyboard won't pair with the Mac via bluetooth. Logitech Options pairing tool says 'Your Mac does not support Bluetooth Smart devices', which I think means is not 4.0+.

I'll persevere as it may be unrelated to this overall issue.

EDIT - Yep, fixed with a reboot. All working!

One thing I noticed in your instructions/video:

AntiHawk wrote:

Hi,

I changed the procedure a bit as NVRAM reset was pain to do as I have firmware password set.

Doing SMC reset instead.

https://www.youtube.com/watch?v=2elFJmqJJtI

---

1. For demo purposes I have already broken my internal BT with CSR 4.0 BT dongle

2. Disconnect CSR 4.0 BT dongle if it is still connected

3. option+shift+bt icon - debug - reset the bluetooth module

4. Run “sudo rm /Library/Preferences/com.apple.Bluetooth.plist”

5. Shutdown your Mac and do SMC reset

1. My procedure is following as I have filevault enabled

1. Start your Mac

2. Wait until filevault login appears

3. Press option+cmd+RIGHT SHIFT for 7 seconds

Number 3. should be option+control+RIGHT SHIFT, not CMD. At least according to the Apple instructions here.

Thanks again for all your work on this.

I also get this issue :(

My only option is to connect the Dongle through this: https://www.apple.com/shop/product/MUF82AM/A/usb-c-digital-av-multiport-adapter

jberian wrote:

Thank you for this amazing info @AntiHawk!

I've bought a BT 2.0 usb dongle (the same exact chipset as yours) but I must be doing something wrong... it's not working for me. Could you please record a video and upload it to youtube?.

When I connect my BT 2.0 usb dongle I see how the BLE icon disconnects, shows an error and then comes back to normal. But I cannot see my MacBook from my Android phone... The only thing I see is a red blink LED on the BT 2.0 dongle. Any clues?

what I used both for breaking it and fixing it was one of these https://www.apple.com/shop/product/MUF82AM/A/usb-c-digital-av-multiport-adapter

I didn't even need to do all the steps, only plug the bt2.0 in, let it search, don't remember if I connected to something, then removed it and rebooted, clear NVRAM and once the pc booted, bt was working again :)

I am using the original Apple cable, this one:

https://www.apple.com/shop/product/MJ1M2/usb-c-to-usb-adapter?fnode=991252f92d2a40afc8b66f3bd32a7e266d95b2f480ad1430d0018901292024de76a18d18503b7c1bb97119bb3750331bdf52aaff248717ab8ab99cf7399a5fa83027245b3a1c0c56d84d89eafbbee2d0bc8c1d48a9bea6c509fb59b3c4dc4e8a

I would recommend trying another Bluetooth Dongle, as my first one didn't work, which was the same as yours. I think trying to find a use Belkin, TP-Link etc might give more of a chance of success.

kelvin_hk_uk wrote:

I'm afraid that Apple might have ignored this issue since this thread is marked as 'solved'.

Apple Engineering does not comment on any discussions here. However, they may read these.

Apple you need to fix this asap!

Use https://feedbackassistant.apple.com or Product Feedback - Apple.

Hi Gordon

The chipset can be identified in the "SystemInformation Tab" / USB Details. See attached screenshot.

In the example, you can see the BCM2045A chipset. The spec of this chipset clearly states, that it is BT2.1.

Some more details about chipsets:

If switching behaviour is set to always, then:

• With a CSR8510 A10 chipset, I can repeatedly "crash" the internal bluetooth.
• Then, with a BCM2045A chipset, I can always fix it.

Boris

T2 does not control BT/WiFi.

Good to know. Given that the issue was surviving the complete re-install of OS, I assumed it was on T2. I guess there are more firmware with storage that persist through disk/OS wipes.

Try Product Feedback - Apple or https://feedbackassistant.apple.com....

I did. I'm still waiting for the response, though.

Exactly same problem here.

Brand new MacBook Pro 16".

I plugged a USB Bluetooth dongle to pass it to my VM - and I lost the integrated bluetooth module.

Have tried everything:

• reset NVRAM / SMC
• Erase my Mac - clean Catalina install
• Bluetooth Explorer still showing no HCI Module
• Boot diagnostic

So have requested Genius Bar appointment this week end :-(

I have the exact same problem with my MB Pro 16". Tried the following:

1. Restore from TimeMachine backup.
2. Fresh install MacOS
3. Clear NVRAM
4. Run Diagnostic tool
5. Install Windows 10

None of the above worked for me :( One option left - return it to my local reseller (no Apple Store in Ukraine).