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: Knock sensor inspection
Note Perform the following test only when directed. Resistance Inspection 1. Turn the ignition switch to LOCK. 2. Disconnect the knock sensor connector. 3. Measure the resistance between the knock sensor terminals A and B using an ohmmeter. If not as specified, replace the knock sens ...

Mazda 6 Service Manual: Service cautions
HANDLING INSUFFICIENT REFRIGERANT LEVEL If an insufficient refrigerant level is detected at troubleshooting, do not charge (add) the refrigerant. Because an accurate amount of refrigerant cannot be determined from the pressure indicated on the manifold gauge, never charge the refrigeran ...