WARNING
Do not leave the key in your vehicle with children and keep them in a place where your children will not find or play with them:
Leaving children in a vehicle with the key is dangerous. This could result in someone being badly injured or even killed. Children may find these keys to be an interesting toy to play with and could cause the power windows or other controls to operate, or even make the vehicle move.
CAUTION
A code number is stamped on the plate attached to the key set; detach this plate and store it in a safe place (not in the vehicle) for use if you need to make a replacement key (auxiliary key).
Also write down the code number and keep it in a separate safe and convenient place, but not in the vehicle.
If your key (auxiliary key) is lost, consult your Authorized Mazda Dealer and have your code number ready.
NOTE
The driver must carry the key to ensure the system functions properly.

To use the auxiliary key, pull out the auxiliary key from the transmitter while pressing the knob.

Keys
Keyless Entry SystemMazda 6 Owners Manual: Drive shaft (mtx) disassembly/assembly
1. Disassemble in the order indicated in the table.
2. Assemble in the reverse order of disassembly.
Clip Disassembly Note
1. Mark the drive shaft and outer ring for proper assembly.
Caution
Mark with paint; do not use a punch.
2. Remove the clip.
Balls, Inner Ring, Cage Disassembl ...
Mazda 6 Owners Manual: Dtc clearing procedure
1. Start the on-board diagnostic test mode.
2. First press the POWER button, then simultaneously press AUDIO CONT button
for 2 seconds or more.
Caution
Before clearing the DTCs, be sure to enter all of them displayed
in the on-board diagnostic test mode in the Audio Repair Order Form. ...