The Mazda 626's immobiliser unit can identify your car keys to prevent theft. You can add additional keys for backups or to replace ones that you have lost. You must know the eight-digit Immobilizer Unit code--which you can obtain from Mazda by providing the serial number--or by using the Mazda software's "Code-Seeker." With the unit code, and the right instruction, you can program Mazda 626 keys in little time at all.
Place the new car key in the ignition bezel, turn it forward to the "On" position, then turn it back to "Lock." Go back and forth between the "On" and "Lock" positions four more times (for a total of five), with no longer than one second between changes.
Turn the key back to the "On" position, then turn it to the "Lock" position within 20 seconds, after the security dashboard lights start to blink. When turned back to the "Lock" position, the rate of blinking will slowly reduce.
Turn the key back to the "On" position, then wait for the security lights to blink the value of the first digit of the Immobilizer Unit word code. When the value of the first digit is reached, turn the key back to the "Lock" position.
Repeat Step 3 until you have completed it for all eight digits of the code. Do not turn the key to the "On" or "Off" position while the security light is illuminated. When the security light comes on and stays on, that means that the pass code has been taken successfully.
Start your car to turn off the security light and exit the programming. Your car should return to its normal state within half a minute or so.
Repeat steps 1 through 6 for up to eight separate keys.