Although the iOS 4.0.1 update was ostensibly designed only to “improve the formula to determine how many bars of signal strength to display” and address other minor bugs, a number of users have reported significantly degraded actual signal strength (not just fewer bars, which may occur with the same signal under iOS 4.0.1) and increased incidence of dropped calls.
Sample reports from the Apple Discussions board include:
- Tetchypete: “Same here. Never had reception issues at home before, since ios 4 I am frequently getting searching and no signal. It’s not just fewer bars it’s an inability to make or receive calls.”
- kit_kat_80: “used to have a really good signal in my flat – absolutely no problem connecting to 3G. Since I upgraded to 4.0.1, I still have the same number of bars, but I can’t connect at all from my flat.”
As we noted previously, while the new update includes a modem software update (which theoretically could result in a change in actual signal strength in some areas), most of these problems are likely due to network settings issues or other temporary problems that occurred during the software update rather than due to the software update itself.
Fixes
In most cases, these issues can be resolved by following the 4 Rs:
1. Reboot (hard reset). Hold down the sleep/wake and home buttons simultaneously for roughly 15-20 seconds, until the screen powers off then an Apple logo appears, which signifies a reboot. Some problems may require (oddly) that this procedure is performed twice.
2. Reset all settings. The reset may restore disengaged hardware components and clear corrupt data that prevents proper connectivity. Navigate to Settings > General > Reset > Reset All Settings. Note that this will erase stored messages, passwords and other information.
3. Restore, but not from backup. It appears that bad holdover data from iPhone backups (especially those created for previous iPhone models) can cause various issues. Restoring as a new phone will delete contacts and other data, but may resolve the problem. To do so, connect your iPhone or iPod touch to your computer, click “Restore” in iTunes, then choose “setup as new phone.”
4. Reseat your SIM card. Simply remove your SIM card, clean it lightly using a dry cloth, ensure that there is no debris in the SIM slot, then reinsert the card, ensuring a snug fit. Instructions for doing so can be found in this Apple Knowledge Base article.