My check engine light stays on, computer error code says my bank 1 cc is going out. I was told by my mechanic that he sees this all the time w/Nissans, only 148k miles on mine. He suggested I run two bottle of stp cleaner through system and change pcv valve, said this fixes problem a lot and may save me hundreds of dollars. Bought the pcv valve, but not sure where it is on my engine? Please tell me where it is and is it feasible for me to change it myself?