OK, Google...yelling.

[Paul Greig]

My car AA unit won't always respond to 'OK Google' but hears every word if I press steering wheel button.

 

[B. Diddy]

Welcome to Android Central! Which car AA unit? Is it factory-installed or aftermarket?

 

[BergerKing]

Sounds to me like the phone sometimes hears the command, but the system is actually better with the voice prompt, which activates the car's internal microphone, which is positioned to hear you better.

 

[mustang7757]

Agree with B.diddy is this stock head unit or aftermarket , some aftermarket mic are problematic