Mazda 6 Service Manual: No.20 noise occurs at idle when vehicle is stopped in all positions/ranges

No.19 excessive shift shock on torque converter clutch (tcc)

No.21 noise occurs at idle when vehicle is stopped in d, s, l ranges, or in r position

Other materials:

Mazda 6 Service Manual: Head Restraints
Your vehicle is equipped with head restraints on all outboard seats and the rear center seat. The head restraints are intended to help protect you and the passengers from neck injury. WARNING Always drive with the head restraints installed when seats are being used and make sure they are pro ...

Mazda 6 Service Manual: Distance Recognition Support System (DRSS) (Some models)
The Distance Recognition Support System (DRSS) measures the distance between your vehicle and a vehicle ahead using a radar sensor (front) while the vehicle speed is about 30 km/h (19 mph) or faster, and if your vehicle approaches a vehicle ahead more closely than what is appropriate for maint ...