Mobile data error - after iOS 18 update - modem firmware 2.15.01

Yes, well known issue now. My experience is on ios18 in UK on EE network. EE isn’t aware of it as a main issue at the moment, though I called them to troubleshoot the issue before realising it was a modem firmware issue with Apple (ohoh Apple!) this is the joy of trying beta products. Hopefully will be fixed soon. Isn’t a massive issue for me at the moment though if anyone finds a fix would be good to know. Think it is a modem firmware issue that can’t be rectified right now.

Same here its horrific

I've been having the exact same problems since I updated my phone to iOS 18 beta 3. Then version 18.1 came out and the problem still persists. Deleting the network settings does not help.

I have the same problem and sometimes it disconnects too many times need the fix asap

However, I found a solution that worked for me:

1.	Update your iPhone to the iOS 18 developer beta.
2.	Then update to iOS 18.1.
3.	Use a computer to downgrade your iPhone to iOS 17.6.

This process successfully resolved the issues with the cellular network and call failures on my iPhone.

I hope this helps!

I still have the same issues waiting on the fix

iOS 18 beta 5 also works for me!

I experienced the same issue after updating to iOS 18 beta 5, where mobile data stopped working. However, I manually set the cellular data network from other phone with same provider , and voilà, it started working again.

Hi,

I am facing the same issue -- updated foolishly to the iOS18 beta on iPhone XS (while abroad) and could not connect to the cellular network at all! miserable a nd stressed me out since i am not home!

I am still working with Apple tech and sent them all of the details they requested but i think i have a temp fix.

IOs18 is messing up connectivity with 5G so when you switch manually to 4G network - it connects fine and everything works --c alls, texts, data without wifi.

How do you switch to 4G manually?

Go to settings -- general> select your cell sim line > turn it on >network selection -- turn off the automatic selection toggle and manually select whichever 4G option is available in your area.

make sure your data roaming is also on along with your cellular data option pointing to the right active line,

Also, what I did last two days (not sure at this point all that was needed! ) but maybe:

1. I erased my phone completely AFTER making an iCloud backup of everything.
2. Restored the IOS using my mac -- does not take too long with wifi
3. Set up my iphone as new -- this is imp if you want to avoid downloading any software glitches that may have been previously.
4. backed up my data using my Icloud -- this took a long time for me given the photos/texts/emails etc.

Hope this helps others!

Hi,

I am facing the same issue -- updated foolishly to the iOS18.0 on iPhone XS (while abroad) and could not connect to the cellular network at all! miserable a nd stressed me out since i am not home!

I am still working with Apple tech and sent them all of the details they requested but i think i have a temp fix.

IOs18 is messing up connectivity with 5G so when you switch manually to 4G network - it connects fine and everything works --c alls, texts, data without wifi.

How do you switch to 4G manually?

Go to settings -- general> select your cell sim line > turn it on >network selection -- turn off the automatic selection toggle and manually select whichever 4G option is available in your area.

make sure your data roaming is also on along with your cellular data option pointing to the right active line,

Also, what I did last two days (not sure at this point all that was needed! ) but maybe:

1. I erased my phone completely AFTER making an iCloud backup of everything.

2. Restored the IOS using my mac -- does not take too long with wifi

3. Set up my iphone as new -- this is imp if you want to avoid downloading any software glitches that may have been previously.

4. backed up my data using my Icloud -- this took a long time for me given the photos/texts/emails etc.

Hope this helps others!

If you're experiencing glitches and lag on your cellular network connection after updating to an iOS version past 18.2, it's likely due to a bug in the new software that could be affecting cellular data handling, potentially causing instability in network connections, especially in areas with weaker signal; try restarting your phone, checking for carrier network updates, resetting network settings, and contacting Apple Support if the issue persists;

Threads regards the issues

https://www.reddit.com/r/ios/comments/1fj6ae3/anyone_else_got_really_slow_mobile_data_speed/?rdt=55290 https://discussions.apple.com/thread/255763551?sortBy=rank

Settings to try

People said it was because of RCS in the new update. Don't worry though, in iOS 18.1 Beta 5, they mostly fixed the issue. It is still a little slow, but at least it's usable. For now, turning off RCS should fix the issue. To turn off RCS, go to Settings > Apps > Messages > RCS Messaging then turn off the RCS Messaging slider.

Also try to reset try to go to Cellular>and reset Cellutar usage statistics and check

Disable background app refresh. Head to Settings, then General, and tap Background App Refresh to switch off unnecessary apps.

Threads regard how to improve you iphone

https://www.magfone.com/repair-ios/ios-18-bugs-fix.html, Conclusion: I call apple, they run diagnostics didn't fix, but I suspect their updates, after ios 18 and ahead, my wife has same issues in 2023 the board has iphone system board has to be replaced, i did also called t-mobile and they done they work, but I still have the issues. I'm really frustated not been able to use applications like google voice, or facetime audio to call people without braking voice, failing to retrieve data, so just finish paying off my phone from carier is a iphone 14 plus, excellent conditions but not celluar network connections stable, also did pay apple care for 2 years and right after cancell the payments with update it has that issues. Relly frustated with apple, it never has issues while Stive Jobs was in charge, I looks they loose track of having realible phones and software