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

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Mazda 6 Service Manual: Precaution
Vehicles with ABS/TCS 1. The ABS warning light, BRAKE system warning light, TCS indicator light and/or TCS OFF light illuminate even when the system is normal. *1 : In cases where the light may illuminate, only when ABS/TCS HU/CM detects that speed sensor of rear wheel is malfunctioning. *2 ...

Mazda 6 Service Manual: Solenoid valve removal/installation
1. Disconnect the negative battery cable. 2. Remove the under cover. 3. Remove the control valve body. (See CONTROL VALVE BODY REMOVAL.) 4. Remove the solenoid valve(s). 5. Apply ATF to a new O-ring and install it on the solenoid valve. 6. Install the solenoid valve in the control valve body. ...