If the selector lever will not move from P using the proper shift procedure, continue to hold down the brake pedal.
1. Remove the shift-lock override cover using a cloth-wrapped flat head screwdriver.
2. Insert a screwdriver and push it down.

3. Press and hold the lock-release button.
4. Move the selector lever.
Take the vehicle to an Authorized Mazda Dealer to have the system checked.
Shift-Lock System
Transaxle RangesMazda 6 Owners Manual: Radiator cap
Warning
Never remove the radiator cap while the engine is running, or when
the engine and radiator are hot. Scalding coolant and steam may shoot out
and cause serious injury. It may also damage the engine and cooling system.
Turn off the engine and wait until it is cool. Even then, be ve ...
Mazda 6 Owners Manual: Clutch master cylinder disassembly/assembly
1. Disassemble in the order indicated in the table.
2. Assemble in the reverse order of disassembly.
Snap Ring Disassembly/Assembly Note
Hold the piston down using a cloth-wrapped pin punch.
If disassembling, remove the snap ring; if assembling, install it.
...