Hi, I have a Honda civic 2003, on a couple of occasions when ive started the car the green key light continues to flash until ive turned off the engine on these occasions when ive returned to the car it wont start? it is not the battery?

 

Likely an immobilizer ring going bad... although the key itself is a possibility. Lastly, even though it is highly unlikely... it could be the ECU or CAN controller not recognizing the key/immobilizer consistently.

 

If the wrong key has been used or the code was not received or recognized by the PCM, the indicator light will come

on for about 2 seconds, then it will blink until the ignition switch is turned OFF.

Large metal objects, key fobs, other immobilizer keys, and other transpondars can interfere with the immobilizer

signal. If an intermittent program is suspected, remove the ignition key from the key ring.

Try the other key to see if it recognizes it.