Q: CarPlay Not Using iPhone Data While Connected

Hi, iAlias!

Thanks for using the Apple Support Communities! Based on the information you provided, I understand that when you connect your iPhone to your car's USB for CarPlay, the iPhone loses its data connectivity. Since data is needed for Maps, Siri, and other functions that CarPlay supports, I know it's important that you have that connection. I've got some information and troubleshooting that may help.

First, check out the following article about CarPlay to make sure you have everything set up properly.

Set up CarPlay to use with your iPhone

I suggest making sure you go through the "Get Help" section at the bottom of the article, as it offers the following troubleshooting:

Get help

If CarPlay doesn't work like you expect, here’s what you can check. After each step, try using CarPlay again.

1. Make sure that Siri is turned on.
2. Restart your iPhone and your car. Depending on your car, you might see the CarPlay Home screen when you turn it on. If you don't, look for the CarPlay logo on your car’s display.
3. If possible, connect your iPhone to a different USB port in your car.
4. Try a different Lightning to USB cable. Make sure the cable is certified.
5. Update to the latest version of iOS.
6. Check your car’s manual for help. You might need to install firmware updates for your stereo.

I would also recommend taking a look over the article linked below, which gives you some information on your iPhone's cellular data settings, to make sure you have the correct settings enabled on the iPhone itself.

About cellular data settings and usage on your iPhone and iPad

If you're still having trouble after going through those articles, I would suggest taking a look at the troubleshooting steps in the following article to troubleshoot your data connection.

If you can‘t connect to a cellular network or cellular data 

Safe driving!