I recently visited the Hyundai ASS for my second service for oil change and the regular inspection of the car.After finishing the visit the car service,I return to my home and park the car.Next morning when I put the Key in "ON" mode a hiss sound appears to be coming for two seconds beneath the car rear.Whenever I put the key in "ON" mode the sound comes but without starting the Engine.If I start the engine and the turn off the engine then putting the key in "ON" mode will not generate any sound.Please help me as I approach the service center there is no sound to be checked as the Engine warms up.They have checked the car and says that there is no problem.The ECU check is not giving any fault.Please give advice if this is common to Grand i10.