iPhone connects and disconnects from Mac

But I do think I solved my problem, by something similar.

On the hunch that the computer was trying to set up a network connection via the phone while the phone was trying to do something else, I went into the network settings and found that in the list of services I had an entry for "Thunderbolt Bridge." I thought it was off, because it was listed as Inactive and the configuration I could see said "Configure IPv4: Off". But to make sure it was really completely disabled I pushed the "Advanced" button to change the configuration details (after clicking the lock icon and authenticating, of course). I changed "Configure IPv6" from "Automatically" to "Manually" and saved that.

After that, connecting my phone to the laptop finally worked. I was just now able to get some pictures off my phone onto the laptop.

I finally figured out the solution to why my iphone kept charging off and on:

I had offloaded / deleted the Music (iTunes) app on my phone. After reinstalling this it allowed me to Trust the computer.

I did what welibelkov suggested:

1. Disconnect your iphone from cable.

2. On your iphone: ->Settings -> General -> Reset -> Reset Location & Privacy (accept all things).

3. Connect your iphone back to cable. (iphone will reconnecting again, don't worry, it will be soon over).

4. iTunes will ask about trust, accept all this.

But was unable to trust the computer cause my Music (itunes app wasnt installed)

I had the same problem. My computer was a late 2014 iMac 27" 5K. Problem started with my iPhone 6 and persisted after I upgraded to iPhone Xs. Things I had tried:

• Restarting many times both iPhone and iMac.
• Changing the USB inlet.
• Using a different USB cable. The problem would stop for a very short time and then return.
• Connecting to my MacBook Pro with the same USB cable. It worked fine. Problem was with iMac.
• Force quitting "usbd" from Activity Monitor.
• Settings>Network> iphone USB> then uncheck the box that says "Disable unless needed"

None of the above worked. Until I contacted Apple Support today. They prompted me to enter this Terminal code:

sudo killall -STOP -c usbd

Problem stopped immediately. I restarted the iMac and things still work fine. Haven't seen how it turns out long-term, though. Give it a try.

This is a cool trick, when your iPhone can’t connect to Xcode (connects/disconnects in a loop):

Sep 11, 2018 8:27 AM in response to MélodyH

Connect your iphone to your Mac.

Go to Activity Monitor --> Search for usbd --> Force quit it.

I have a similar issue and believe it's a power issue.

When I plug my iPhone XR to my 2015 MBP 15 via a USB cable, it keeps disconnecting and connecting. Doesn't happen on any of my MacBook Airs with the same cable, only my MBP 15.

My imperfect solution is to:

1. Make sure the mac accepts the phone: on iPhone Settings -> General -> Reset -> Reset Location & Privacy (accept all things).
2. Plug the iPhone through an external USB hub that uses external power supply (mine is the TB display)
3. On phone, trust the mac connection

Now I can transfer / sync my phone with my mac.

Yes, it worked! With one extra step -- My iPhone kept asking if I should trust the computer: the alert box kept popping up and disappearing as the phone repeatedly connected and disconnected from the computer. Be quick! As soon as you see the alert on your phone, click Trust. Worked for me. Thanks, Welibekov!

This was one of my struggles and I searched several times for an answer. One comment was finally correct! It’s because the battery is too low! If my phone was under 50% then it would essentially freak out and keep connecting and disconnecting instantly. I think it’s because it was struggling to charge and connect to the iMac. So after it’s charged to a good amount, mine does not do it anymore. I hope this helps other frustrated people solve it. 🤞🏻❤️

I FIGURED IT OUT - so I have a 2015 MacBook Pro and an iPhone 11 Pro Max. Both USB ports gave me the rapid disconnect/connect, and was so frustrating. Tried EVERYTHING - reformat everything, reset everything, BUY A NEW IPHONE, yet nothing worked. THen work gave me a new iPhone SE and it didn't have an issue.

So I thought, maybe it's to do with the power draw/output on the USB port vs a powerful iPhone!

So I got a Ethernet USB adapter that has a USB port on it, and plugged my iPhone it that way.

IT WORKED - no more rapid disconnecting! So it's not an elegant solution because Apple are Apple and we love dongles. But at least I can finally backup and sync my iPhone!

Next problem to sort out: Album Art and songs repeating the last 30s!

This worked for me (going to network in system preferences on computer, click on iphone usb, uncheck box that says disable when needed) when nothing else did. iphone xs max with ios 15 connected to 2015 macbook pro 15 inch running big sur 11.5.1

For the last year nothing else corrected the rapid on/off when phone was connected via usb to computer. This fixed it.

This is a notorious issue. I have faced it multiple times on my iPhone.

Troubleshooting steps range from killing a Mac process to resetting your iPhone. Faulty cables and lightning port could be the culprit.

I found success after following the below steps- 

1. Check cables and ports. 
2. Reset iPhone Location & Privacy Settings.
3. Change Finder Preferences.
4. Restart the USBD process by heading over to Activity Monitor (This fixed iPhone disconnected with Mac issue for me.)
5. Reset SMC/NVRAM on Mac. 
6. Create a new admin account on Mac. 

Let me know if you were able to fix this issue. 

In depth information:- iPhone keeps disconnecting from Mac? 7 Fixes

I had my iPhone doing the same thing, connects and disconnects from Mac, I tried all options mentioned in the forum without lack. Recently I have moved my office to another room and had shut down Mac and disconnect all cables from it, left it off overnight without any cables connected to the Mac, even power cable disconnected from the wall outlet. The next day reconnected all cables and now my phone charges with no problems. I had to Trust my device first.

I came across this yesterday with my daughter's 8 month old MacBook Air and iPhone 7. When she plugged it in it constantly connected/disconnected. We tried

• multiple lightning cables
• multiple ports on her MacBook
• her phone charges fine with the same cable when plugged into the wall
• her phone and same cable works fine when plugged into another MacBook Air
• My Galaxy S7 charges ok when connected to her MacBook Air
• My brand new iPad also has the same connection issue when connected to her MacBook
• We then tried a different lightning cable that came with my iPad which appears to be slightly thicker, it charged both the iPad and her iPhone OK on her MacBook!
• I later found that if her phone was charged at 71% any of our lightning cables would charge it, when her phone was at 23% only my iPad cable would charge it.
• The iPad still wouldn't charge with the older lightning cable even when at 81%

So I'm thinking that an iPhone that is "more" flat may draw a higher charging current from the USB port. Not sure if the older cables are slightly worn out/ damaged and cannot provide the current, or there is some other tolerance problem, but a newer cable worked for us. That doesn't really explain why it worked with a low battery percentage on another MacBook though with the original cable. There is something weird going on.

Try Force Quitting the USBd process on your Mac.

1. Open Activity Monitor on your Mac (in Applications>Utilities)
2. Search in the search bar for USBd
3. Double click on USBd and Quit / Force Quit the process.

Hopefully your phone should then charge normally.

I have no idea what this USBd process is and you try this at your own risk - just saying it worked for me with no problems. The phone charged and sync'd perfectly with itunes afterwards

Connect your iphone to your Mac.

Go to Activity Monitor --> Search for usbd --> Force quit it.

sudo killall -STOP -c usbd

That's worked for me!