2008 Honda Element Question: Check engine light ON in Honda City

I have a 2008 Honda City ZX Model (India). recently the check engine light started glowing. during the cold start at the time of starting the engine all lights goes off, however when the engine gets slightly heated and the Blue CF engine lights goes away the check engine yellow light comes on. After covering approx 3-4 kms when youagain turn off the engine and restart the check engine yellow light disappears and never comes backuntil the vehcile is again back to a cold start. what could be the issue. is it something major or minor. what could be an approximate cost