Jonty's iPhone Help

3GS reboots during telephone calls



The chances are you're here and reading this webpage because you have a problematic iPhone 3GS and have seen my posts on the Apple support forum offering help.  I am (well, I used to be) just a fellow iPhone 3GS user but I'm more than happy to share my findings and experiences in hope that you too can solve your issues.  But I would like to stress that I do not take credit for the basis of the fix as I'm simply sharing my own experiences and that of many, many others that have provided feedback.

As for this webpage, well, previously I had invited anyone with 3GS 'rebooting during calls' issues to email me directly and I would then provide all the below information and offer extra assistance if I could, but personal circumstances changed, I've since moved to Android/Samsung and unfortunately I don't have the necessary time to offer and maintain such dialogue, hence why I've compiled everything here and will keep it updated as best I can.  Having personally helped in excess of 1,000 3GS owners fix this issue I'm sure this webpage will maintain that trend.

This isn't the shortest webpage in the world and whilst I could perhaps apologise for all the detail there really is no need as I simply want to give you ALL the information I feel is relevant (and structure it into useful and informative chunks!)  At this point you have a choice; you can continue to read on and learn more about the problem and fix procedure, or if you prefer you can jump straight to the section called The fix process and begin fixing the problem, but I would strongly suggest reading on to gain some insight into the problem.

Lastly, this fix is based and reliant on jailbreaking.  If you cannot or do not want to jailbreak your iPhone then you CANNOT run this fix (jailbreaking is a necessity for this and NOT a choice I'm afraid).

All the very best, and good luck!

Jonty  :o)

PS: Page last updated on Friday 22nd March, 2013.

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Essentially I'm focussing on the 'reboot during calls' issue ONLY with the iPhone 3GS running iOS 4/5/6.  If you're looking to cure other problems then I'm afraid you're looking in the wrong place.  I'm solely a Windows user (with no Mac access) so given this and the calls/reboot issue I've made the below assumptions so you know what to expect from me.  If your circumstances differ then Google is your friend if you need additional help.  So, I'm assuming...

> You have an iPhone 3GS (not any other model)
> You are running iOS 4/5/6 (not each version can be fixed, see further down)
> You ONLY suffer from reboots during telephone calls (i.e. reboots/crashes/problems at other times may indicate another fault)
> You are prepared to jailbreak your iphone 3GS (this will VOID any Apple or third party warranty)
> You have a PC using Windows
> Your PC has iTunes and your 3GS is synced/backed-up
> You are reasonably technical but essentially prepared to read instructions and 'fiddle' with software and your iPhone

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History and Success

The 3GS 'reboot during calls' problem first occurred mid-2010 when Apple released iOS 4 (with OS 3.x there were no such issues).  Although a world-wide problem the frequency and degree of rebooting varies from person to person.  To this day none of the iOS 4, 5 or 6 updates have cured the problem, nor has Apple officially recognised or communicated about the fault, which is gravely disappointing.  Given my own involvement and experiences I'm of the opinion that a batch/design of specific 3GS batteries have logic/circuitry which is incompatible with iOS 4/5/6.  On the few occasions this fix has failed to work it's transpired that other reboot and crashing issues have been present (and either a new battery has been the cure or the iPhone itself has had other hardware issues).

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Jailbreaking and Before you begin

If you're new to jailbreaking then the term itself may seem suspicious, but it's not.  It's just about running extra code/software in tandem with Apple's iOS.  As a result you have more control over your iPhone and can choose to do more with it, e.g. themes, sounds, tweaks, and other apps.  Your iPhone MUST be jailbroken so that the root file system can be accessed for the fix, but afterwards you can leave it at that.  And make sure that your iPhone is fully synced/backed-up BEFORE you begin (and make any other backups/copies as you see necessary).  Whilst the jailbreak process is relatively straight forward, you never know what might go wrong.

NOTE: This fix has worked for all bar a handful of people, so do consider that nothing is guaranteed.

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The fix process - the Jailbreak

To begin with make sure your iTunes software is the latest version, so update/download if necessary.  Next, study and/or download the necessary jailbreak solution for your 3GS given the iOS you're running.  Personally I like the 'untethered' flavours which means you don't need to use your PC to restart/reboot your iPhone if the battery dies, it's switched off, needs to be restarted, etc.  Tethered jailbreaks are okay and will do the job but if your iPhone needs to be switched on again (restarted/rebooted) then it MUST be connected to your PC, so not ideal.  So, make sure your chosen jailbreak program is compatible with the iOS installed on your iPhone 3GS and get stuck in...

iOS 6.1.3

Released on 19th March, 2013 and available for the 3GS as well as all newer models.  As of 22nd March too early to know if reboots still exist and no jailbreak methods available.

iOS 6.0 - 6.1.2

iOS 6 was released on 19th September, 2012, and there's a fantastic untethered jailbreak called evasi0n which works with every version from 6.0 to 6.1.2.  The tool is extremely easy to use -- just connect your iPhone, run the software and follow the on-screen prompts!  Wow!

iOS 5.1.1

As of 4th June, 2012 there are untethered jailbreaks Absinthe 2.0 and redsn0w.  If you're using a tethered jailbreak then search Cydia for 'Rocky Racoon 5.1.1 Untether' to untether it.

iOS 5.1

There is no untethered jailbreak available, but there is a tethered jailbreak available using redsn0w.  This is not ideal because you'll need a PC each time you want/need to restart or reboot your iPhone.

iOS 5.0.1

You will jailbreak using a tethered solution first followed by an un-tethered patch afterwards... and then

iOS 5.0

No jailbreaks available.  You'll need to - somehow - get one of the more recent iOS versions onto your iPhone.

iOS 4.3.4 and 4.3.5

No untethered jailbreaks are available (that I know of).  I still cannot help at this time so you will need to perform your own research and/or wait for good jailbreak solutions to become available (or ideally upgrade to iOS 5/6 or downgrade to 4.x, if you know how to).  It's known that with the release of iOS 5 that jailbreaks for 4.3.4 and 4.3.5 have been ignored.

iOS 4.3.3

This is for iOS 4.3.3 ONLY.  Use your iPhone 3GS to visit the link and jailbreak directly from your device! This is the easiest and best...

iOS 4.3.x (but not 4.3.3)

The RedSn0w jailbreak is great because it updates what you already have, i.e. no need to wipe your iPhone clean and install from fresh, so this is good... or
Readme at

iOS 4.2.1

My 3GS was running this version up to the point when it was formally retired (as a backup/test device it's now running iOS 6.0.1).  iOS 4.2.1 and this jailbreak were great with the only negative that some apps relied on iOS 4.3 or newer. and also check out

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The fix process - Installing Cydia, etc

Once you've jailbroken your iPhone 3GS make sure you install Cydia if it's not already been done (there's normally a new icon on your iPhone screen to do this).  As well as installing essential code, Cydia is also another app store which has lots of useful things.  Next we need to be able to access your 3GS file system.  There's two ways to do this; via the data cable using iPhoneBrowser (nice and simple) or via wireless using WinSCP (which needs extra steps so you can use it).  Both are detailed below...

To use iPhoneBrowser / data cable, download from the link here (and then skip to Replacing the Mobilewatchdog file)...
To use WinSCP / wireless, download from here (install it on your PC but don't run it just yet)...

Then launch Cydia (on your iPhone) and in the home screen there should be an option called 'OpenSSH Access How-To'.  Have a read and install the code (tap the link).  It's not needed for the fix but ideally you should also change the admin password on your iPhone (for use with wireless connections).  To do that I downloaded and used a program called Putty.

To get your 3GS and PC talking to each other via wireless you can use this link as a reference (but don't worry about the permissions part, once you're connected is enough I found)...

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Replacing the Mobilewatchdog file

Next comes replacing a special file or two (depending on your iOS).  I've attached copies which you will need to 'save-as', rename, and put into the places as per the below.  Please note the filenames of the attached files MUST be adjusted.  Now, using iPhoneBrowser or WinSCP do the following depending on the iOS being used...

For iOS 5 and 6...

Save these files to your computer... mobilewatchdog5 and Info.plist5

From the 'root' browse to /System/Library (in your iPhone) and make a backup/copy of the 'Watchdog' folder.  Inside 'Watchdog' delete the folder called 'MemoryMonitor.bundle' (but DO NOT delete ThermalMonitor.bundle.  Then copy the mobilewatchdog5 and Info.plist5 files into /System/Library/Watchdog.  Finally, rename both files by removing the '5'.  NOTE: The actual filenames should be mobilewatchdog (no extension) and Info.plist.

For iOS 4...

Save this file to your computer... mobilewatchdog4

From the 'root' browse to /System/Library/SystemConfiguration/mobilewatchdog.bundle (in your iPhone) and make a backup of the mobilewatchdog file (only), rename the version in your iPhone so you still have it there, and finally upload the mobilewatchdog4 file.  Once uploaded rename by removing the '4'.  NOTE: The actual filename should be mobilewatchdog (no extension).

For iOS 4/5/6... you're almost done...

Lastly, disconnect, unplug everything and REBOOT your iPhone (if you do not reboot your iPhone the fix will not work).  And now you just need to test by making or receiving calls of a good length, and hopefully all will be okay for you!

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Useful links

iOS history/details

iOS firmware downloads or

Information about GreenPois0n

Information about Redsn0w

Changing the battery (the last resort!)

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