Peugeot 307CC 2005 ?

hello there i have just purchased a 307cc 2005 4 weeks ago done 40k, and the depollution warning light came on as this happened on the friday i was going to book it into peugeot on the monday however on the sunday the light went of, however 5 days the later the warning has come back on and at the same time the ABS/ESR warning came on so i pulled over turned the car on/off the ABS/ESR warning has gone but the depollution warning is still on, does the computer record all faults so all of these will show up on a diagnosis machine and does anyone have any idea why this is happening?