ok so i had a code up 501 i think speedometer/performance sensor so we replaced it the speedometer started working again now its working in spurts it will work for a little then when the car geets runnin it will stop working then when u let the car sit and go to it the next day it will work then it will stop again the sensor we bought was brand new cause we dont deal with used parts but i dont understand i made an appointment to get the whole speed sensor to get re wired i dont wanna ahve to do that if someone else has a clue of what it might be. Another thing how long does it take ready codes to clear after you erased check engine codes?