With iPhone antenna issues still attracting a lot of attention, problems with the iPhone 4’s proximity sensor have largely been flying under the radar. A number of users have observed that the proximity sensor on the iPhone 4 is calibrated differently than on previous iPhones. The result is that the phone doesn’t always recognize when it’s being held up to a user’s face, prompting users to inadvertently end or mute a call during the middle of a conversation. Compounding matters, some users note that the iPhone 4 screen will shut off during a phone call, but won’t turn back on once the call ends or the phone is removed away from a user’s face.
Much like the widely publicized antenna problems, proximity sensor issues on the iPhone 4 don’t appear to affect all users. Still, MacRumors points us to a Macworld article which offers some work-arounds which appear to alleviate the problem.
Many affected users report that either a Settings reset or a hard reboot fixes their problem. One Apple support thread recommends that users open the Settings app, then go to General -> Reset, and choose “All Settings” at the top (note: this will not erase your apps, media, or other data—that’s what the “Erase All Content and Settings” button just below this option is for. “Reset All Settings” just reverts any Settings preferences you’ve customized back to their factory defaults). One Twitter follower, Brian Partridge, reported that AppleCare told him to just use Reset -> Reset Network Settings, not all settings, and it worked.
Another option to try and jump-start the proximity sensor again is to do a soft or hard reboot. A soft reboot is simply holding the power button until the red power slider appears, then sliding it to actually power down the phone. Once it’s done, hit the power button again to restart it…
[For a hard reboot] hold the power and home buttons until you see the display go dark and Apple’s logo appears.
Apple has yet to address the issue, but don’t be surprised to see it resolved in an upcoming software update.