What's the problem and solution? on 1996 Nissan Altima

I heard a noise inside the engine under the oil hole cap, i went to make the smog sheck a told me that the knock sensor code it was flashing, and vibration and drone when i start the engine and when i drive the car until a few miles the vibration and drone dessapear.

1 answer
The flashing Check Engine or Service Engine Soon Light is not a knock sensor code, that is a Misfire Code. read this - > http://repairpal.com/misfire-what-does-it-mean

you may also have a knock sensor code, but that will NOT make your CEL flash on a 1996 car. By the way, how is your oil level?