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: i-ELOOP
i-ELOOP is a regenerative braking system. When you depress the brake pedal or use engine braking, the kinetic energy that occurs is converted to electrical energy by the power generator and the converted electrical energy is stored in the rechargeable battery (capacitor and battery). The store ...

Mazda 6 Service Manual: Battery recharging
Warning Keep any flammable away from the battery, otherwise evaporated gas of the battery fluid may catch fire, and cause serious injury or death. Caution When removing the battery, disconnect the negative battery cable first and install it last to prevent damage to electrical compo ...