Question:Q:Apple CarPlay screen is pixelated when phone is connected

That would be a question to address to your car dealer. They are the ones that maintain CarPlay in the vehicle. While Apple provides the software, the vehicle manufacturer implement it on their devices. They should be able to troubleshoot this.

Remove your car from CarPlay. Power the phone off and back on again, then try pairing it with CarPlay again. There are really no other settings for CarPlay to make.

You're welcome.