Soo I got my jeep looked at by dealer they did a diagnosis on it said cats probaly went out. I replaced the spark plugs and wires the old one were all gaped weird and I don't think they ever been changed has 79 thousand miles on jeep the fuel injectiors went out awhile ago so did the egr valve had them replaced.the 420 code doesn't show up either does the check engine light but if I'm to turn accessorie on and everything lights up and turns off but the check engine light flashes is the code still there am I still gonna have replaced the cats