If there is an AutoZone close by you can go there and they will pull the computer codes for free. If not, you'll have to visit a repair shop with the ability to do so; they typically charge for this.
P0455 code for mazda Protede... Evaporative Emission System Leak Detected (gross leak/ no flow)
Trouble code P0400 means:Exhaust gas recirculation-flow malfunction
Unplug the baterry, press brake for 20sec, done :)
Trouble code P1507 means: Idle air control (IAC) underspeed error
Trouble code P0421 means:Warm up catalyst system efficiency below threshold
Check engine is an error. You have to go at a garage to see what is the error code, then correct the problem.
With a scan tool.
If you have an OBD (On Board Diagnostics) scanner, you can read the error code and reset check engine light. Obviously, if the problem is still occurring the light will come back on. Most of the chain autoparts places will read and reset the OBD for you for free. the scanner read #141
The computer doesn't allow to start the engine. Check the error code.
You need to check your engine. The computer has detected a problem with the engine management system and the light is letting you know that is has error codes stored.
check your engine
Pretty simple connect an obd2 scanner and it will pull the error codes for the check engine light then look up the error code and diagnose and fix your problem