Because its system is closed to end-user access, most traditional troubleshooting methods don’t apply to the iPhone or iPod touch – you can’t trash a program’s preferences files or reinstall a standard program on iOS, for instance.

A few remedies are available, however. And since the list of possibilities is very short, you don’t need a lot of expertise to try them. Here are the things you can do to try to recover from various iOS maladies…

1. Force Quit

In iOS 4, whenever an app freezes, you can force it to quit from the multitasking shelf – you can bring this up by double-clicking on the iPhone’s Home button. Press and hold on the offending app’s icon until it starts to shake, adding a red minus button to the upper-left corner. Tap this to quit the app.

Alternatively, while in the problematic app itself, you can press and hold down the Sleep/Wake button on the top of your device until the red Slide To Power Off slider appears. Release the Sleep/Wake button, but do not power off your device. Hold down the Home button for about six seconds. This should force the app to quit and return you to the Home screen.

2. Restart

If the problem persists, try restarting. Press and hold the Sleep/Wake button on the top of your device until you see the Slide To Power Off option, then drag the red arrow to the right. Wait a moment before turning your phone on again – it will take about a minute to reboot. Restarting is the most effective fix for most freezing and crashing problems, and is recommended as a first step for most issues, including excess battery consumption, crashes, and sluggish performance.

3. Forced Restart

On occasion, your device may be so gummed up that the Power Off slider won’t ­appear after you attempt a regular restart. This means it’s time for some muscle. Hold down the Sleep/Wake and Home buttons simultaneously until the Apple logo pops up, signalling a forced restart.

4. Reset

When problems persist after a restart, the culprit may be corrupted settings or data on your iOS device. If so, one fix is to delete the information, and re-enter or resync it. Tap the Settings icon on the Home screen, select General, and then tap on Reset. In the screen that appears, you’ll see multiple reset options. Only the first two are of interest here.

Reset All Settings Apple makes a distinction between settings and data. The latter consists mainly of the information that gets synced with your computer, such as music, photos, and contacts. Settings consist of the choices you make for the iOS interface and its native applications – for example, the cities you choose in the Weather program – but they don’t include your third-party applications. In theory, tapping on the Reset All Settings button reverts your settings to their original values, while leaving your data untouched. In practice, however, some settings – such as stock choices and wallpaper selection – may not reset.

Erase All Content and Settings As its name implies, this option erases both your settings and your content (data), and returns your device to its original condition when you first activated it. You can now recreate your settings. The content is automatically reloaded the next time you sync your device.

5. Replace data

If you suspect there’s a problem with the data (contacts, calendars, Mail accounts, or bookmarks) on your device, a useful option is to replace it with fresh data from your computer, rather than merging the two data sets, as would normally occur. To do this, go to your device’s Info tab within iTunes, scroll down to the Advanced section, and select the types of data you want to replace (Contacts, Calendars, Mail Accounts, and/or Bookmarks). You’ll need to confirm that these options are disabled once the sync is complete to resume normal syncing next time around.

You should note that once you take this step, you’ll lose any new data you’ve entered on your device since the last time you synced it. To be on the safe side, take a moment to sync your computer and iPhone or iPod touch before replacing its data.

6. Restore

If none of the above has proven successful, it’s time to bring out the big guns: erasing your device’s entire contents, including its operating system, and installing a fresh copy of iOS. This method is also useful should you need to transfer your data from a defective device to a replacement one.

Restore from Backup Before you start, you should sync your device one more time and let it run a full backup. This will allow you to save any of the data you’ve stored with your third-party programs. If your device isn’t in a usable state and you can’t make a new backup, you’ll still have the option to restore from an earlier backup. After the software is restored, iTunes will ask if you wish to restore from a backup.

To start the restore process, connect your device to your computer, open iTunes, and select your iPhone or iPod touch from the Devices list. In the Summary screen that appears, click on Restore. iTunes will then download a software update for your device. This will contain, among other things, the latest version of the operating system. After the download is complete, your device’s original factory settings will have been restored. At this point, a dialog box will ask if you want to set it up as new or restore all the data and settings from a backup. Unless you believe your backup contains corrupted data, you should opt to restore.

After this process is complete, sync your device to get back your content (music, videos, synced photos, calendar items, contacts, and apps). With the sync finished, your device should be restored (although email and Wi-Fi network passwords, stock selections, and photos taken with your device aren’t restored).

Restore from Scratch If you try the restore method described above and find you still have the same issues, it may be that the settings or data currently on your device became corrupted sometime before your last sync. Restore it as above, but do not restore your backup. Instead of restoring the backup, tell iTunes to treat your device as new. Give it a name, reinstall all of your applications from scratch, and then sync your music, videos, and other content. This is as close as you can come to starting with a factory-fresh device, and represents your best chance at increased stability.

When you do this with an iPhone, it will tell you that it needs to be activated – this just means it needs to reconnect with the mobile network that you’ve already activated your device on. This should happen automatically within a couple of minutes.

7. Recovery mode

If your device is unable to even start up successfully, a message may tell you to connect to iTunes (see Duck and Recover screen, right). After you hook up your device, another message will appear, telling you that “iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes.” If this happens, proceed with the restore, as described earlier, and hope for the best.

You can also force your device into recovery mode. This can be useful, for example, if your iPhone or iPod touch can’t get past the Apple logo portion of the boot process or is stuck in an endless loop of restarts that prevents it from appearing in iTunes.

To force a recovery, hold down the Sleep/Wake and Home buttons – as you would do for a forced restart – but continue holding them down after the restart begins. After about 25 to 30 seconds, the recovery mode message should appear. You can now connect to iTunes and restore. If you decide not to restore from recovery mode, you can exit by holding down the Sleep/Wake and Home buttons for six to 10 seconds. No data will be erased during a forced recovery.

If your device still fails, it’s time to take it to Apple for a service. You can locate the nearest Apple Store or Apple Authorised Service Provider at