I am new for this forum but I am not new for RX8. I have been using RX8 2004 model for more than a year and few days back the card does not start. It can turn on the pannel and everything else is working but engine is not running. when i turn the key to start, I can see the red (Key) from the dash board starts blinking.

What is the problem? how can it fix? Do i have to cut a new key and replacing the ECU as well?

Please help!

 

You might need a new battery. Get it checked.
Try searching "blinking security light".

 

https://www.google.com/search?q=site...sm=93&ie=UTF-8

 

If you have the advanced Key for your RX-8 you might need to replace the battery in the advanced key. the same thing happened to me and I had to replace my key's battery.

If you have a physical key that you use, I was told by my local Mazda dealership that it can also be a problem with the immobilizer system.

These are just a few things that I have been told that could fit that description, I will be honest when I say I am still learning about my Rx-8 and am by no means an expert.

 

Looks like an immobilizer problem.
Do you have another key/remote? Try it if you do...otherwise try resetting the ecu and then see if it works. You might have to get a new key coded at the dealer or get a new key reader coil