2002 Cadillac Deville
my service engine soon light came on. I hooked it up and the code was p0308, # 8 spark plug was fouling. My mpg in town and highway were 10 & 16. I replaced the plugs and my mpg went to 17 & 21. I took the battery cables off & my service engine light still will not go off. How do you get the light to stay off. My car seems to run fine now.