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: Dtc b1318
Caution When attaching the tester lead to the ABS (ABS/TCS) HU/CM harness connector, the SST (49 G066 001) must be used. (See ABS (ABS/TCS) HU/CM INSPECTION.) Diagnostic procedure ...

Mazda 6 Service Manual: Woofer inspection
1. Inspect for continuity between the audio amplifier connector terminals and woofer connector terminals using an ohmmeter. If not as specified, replace the related wiring harnesses. 2. Verify that there is battery positive voltage at the woofer connector terminal A (4SD) or C (5HB) u ...