i did a elf diagnostic today and this is what i came up with

front left heated o2 sensor

front right heated o2 sensor

knock sensor

egcr soleniod valve

know i have a question i understand that the soleniod valve disperses toxic gases and such and is only ope at certian times like cruise control (if i am incorrect correct me)

know here is my other question could i be getting these codes do to not having had an exhaust on the car for a while, like 6 months??

would this cause these codes and i understand it is not good for the car in the long run but am i hurtuing it drastically

thanks, ROSS