Hello, Thanks in advance for any and all help that you can offer. I have a 99 accord Lx. I am getting a p420 error. "your cat is operating below specified...blah blah blah..The check engine light was on. I have replaced the cat and the O2 sensor in the cat. I reset the code and the light was off for about 30 miles. However the light has returned. Would anyone have any ideas what else could be causing the light to return? Also, I have been burning standard 85 octane fuel and have read that better fuel may relieve this issue.
Any feedback on this topic would be appreciated.