Hello-
I have a 2011 Nissan Rogue w/ 135k miles. A month ago, the CEL light popped up and scanned P0420 code. "Catalyst System Efficiency Below Threshold Bank 1".
Had it checked by a local mechanic and said they would have to replace the whole intake manifold and exhaust assembly (nearest to the engine)- Projected cost= $1k+. I held off since its functioning as is with no issues. A few weeks later the light turned off. We drive it around 400miles per week- mainly on highway. CEL came back on 2-weeks ago, then on Tuesday the light turned off since.
What could be the issue? Could it be a dirty O2 sensor?
I've read and watched some vids of cleaning certain parts there, but would like to confirm and next steps to look into.
Thanks in advance. MJ
Even a slightly bad tank of gas can do that the stupid computers will trip inefficient catalytic converter when it gets below 95% efficiency. Personally I haven't been working at 95% efficiency for years. As long as it runs fine don't waste your money and if it needs a yearly inspection a lot of times you can reset the code drive it and then get it reinspected I've done that lots of times in Texas. Why on Earth would somebody need to spend that kind of money when a car runs fine
