To turn Bluetooth back on, tap the Bluetooth icon once again.You'll know Bluetooth is off when the icon is black with a gray background. Open iTunes if you have a PC or Mac running Mojave 10.14 or earlier.Using a Lightning cable, plug your iPhone into a USB port on your computer.How To DFU Restore An iPhone SE, 6s, Or Older To turn Bluetooth back on, say, 'Turn on Bluetooth.'.To turn off Bluetooth, say, 'Turn off Bluetooth.'.Open Siri by pressing and holding the Home button (iPhones without Face ID) or the side button (iPhones with Face ID) until Siri appears, or by saying, 'Hey Siri.'.You'll know Bluetooth is on when the icon is white with a blue background. Open Finder if you have a Mac running Catalina 10.15 or newer. It doesn’t matter if your iPhone is on or off.