How to use Siri in CarPlay with or without your voice
AppleInsider -

Being able to make a request using Siri while driving helps keep your eyes on the road, but just asking for Siri may not work on older cars or in certain other circumstances. Here's the fix. For most people using CarPlay, being able to call the vocal assistant Siri up by simply saying its name -- or preceded with "hey" -- is a great convenience. From asking for directions to checking where you need to go next, it makes driving safer. Occasionally, however, you may find Siri doesn't...

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