Hi Guys, In the past two years I have replaced my speed sensor when my odometer when out and that fixed the problem. About 6 months later I was misfiring, so new spark plugs. And that seemed to fix the problem. Now I believe both issues are back. Using the key trick, its throwing p500 and p303? I can go ahead and fix these issues again, but is there some overlying reason why these might be failing??

2003 Dakota
Six cylinder

Thanks,