Knock sensor help

[vicko]

ok so i know i'm going to get flamed for this...
so not too long ago i changed my own oil. i have done it before and only put in the recommended amount of oil, which is 3 quarts. each time was synthetic blend, so the last oil change i had i took it somewhere because i was lazy and the cost was cheaper than i could get the oil (blend as well) and filter. so the last time i did it i used full synthetic except i put more oil than i was supposed to, and the 2nd time i drove the car my check engine light came on. since then i've drained some oil, reset the code, but the light still comes on. i have to get my car smogged soon (like today haha) and i need to know what to do besides maybe test/replace the knock sensor. just giving all the details in case it matters. did i cause any long term damage by putting too much oil in?