1. If not as specified, loosen the fuel-filler lid installation bolts, and reposition the fuel-filler lid.
2. Measure the gap and height between the fuel-filler lid and the body.
Clearance
a: 1.7-3.7 mm {0.067-0.145 in} b: -0.5-1.5 mm {-0.019-0.059 in}
3. Tighten the bolts.

Fuel-filler lid and opener removal/installation
BumperMazda 6 Service Manual: Master cylinder disassembly/assembly
Caution
If the master cylinder body is damaged, replace the unit as a
component. When securing the master cylinder in a vise, tighten only the
flange of the master cylinder.
1. Disassemble in the order indicated in the table.
2. Assemble in the reverse order of disassembly.
Stop ...
Mazda 6 Service Manual: Front door lock actuator inspection
Door Lock Actuator
1. Disconnect the front door lock actuator connector.
2. Apply battery positive voltage to the front door lock actuator terminals
and inspect the operation of the front door lock actuator.
If not as specified, replace the front door lock actuator.
With double locking ...