Remaned PCM installed in vehicle. Unit flashed properly. Unit accepted key code. Now. Immobilizer dash light comes on when key is turned to start, even after key code was accepted.

SOURCE: Mazda 323 2002 Sting Immobilizer

Fcuk I got same problem with my Mazda 3 year 2004. Noone can help me at all !!! Even in Mazda they have no idea where is problem. For me it is at the moment only in cold weather. I cannot get throught immobilizer. After few turns it works, but not always (only when its bit warmer). I found out that if it is warmer, and I turn on ventilation for a while after it will let me go! Immobilizer starts flashing ... after few more minutes and turning key few times it will let me go !!! Please write me to [email protected] if you will know updates... I am desperate , cannot use my car in winter at all or cold weather. In summer works fine

SOURCE: PCM Troubleshooting Check light on with no code reader power

You can't jump the connector to get codes on OBD II. (Pre 1996) Try hooking back up you code reader. If it doesn't communicate, check the fuse for the cig lighter. This fuse should also power up the diagnostic plug.

SOURCE: Turn key and it doesnt fire

one way to find out. spray starting fluid in the intake then try to start. if it starts then your problem is fuel related.

SOURCE: immobilizer

If there is a blinking car icon with an "X" over it. This icon means the Immobilizer has been activated and hence won't allow the car to start. It could be due to a bad SCU, Start Control Unit. The SCU is actually the ignition switch on these cars.
Most of the time it's triggered by the anti-theft system..You can try this trick i learned that the dealers won't tell you...try locking and unlocking of the doors five times with the remote to reset the immobilizer and see if this helps.
Good luck..i hope this helps...please take a minute to rate me a fixya.

SOURCE: Engine won't start. Dash lights flash rapidly when key turned.

the battery says 12 volts but may be dropping to 4 or 5 under a load...i would suggest jumpstarting the car and see what happens.the battery should read in the high 12 volts and not less than 9.5 under cranking. the dash lights go out on your car when starting,and the alarm will go off ,and disable the ignition if the voltage is too low in cranking the car because the computer will shut it down and activate the anti theft.....check your battery posts are tight. best of luck