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: Foreword
Caution When the engine does not start or stalls and the following DTCs are not indicated, go to engine symptom troubleshooting. Note When the immobilizer system is defective, the engine cannot be started. If engine condition is normal but light stays on, inspect for short circ ...

Mazda 6 Service Manual: Locking, Unlocking with Auxiliary Key
Turn the auxiliary key toward the front to lock, toward the back to unlock. To lock All doors lock automatically when the driver's door is locked using the auxiliary key. To unlock The driver’s door unlocks when the auxiliary key is turned briefly to the unlock position and then immediatel ...