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: Dtc c1145, c1155, c1165, c1175
Caution
When attaching the tester lead to the DSC HU/CM connector the SST
(49 G066 004) must be used.
Diagnostic procedure
...
Mazda 6 Service Manual: Curtain Air Bags
The curtain air bags are mounted in the front and rear window pillars, and the
roof edge along both sides.
When the air bag crash sensors detect a side impact of greater than moderate
force, the curtain air bag inflates quickly and helps to reduce injury mainly to
the rear outboard passenger' ...