Check Engine Light Code P0420

Hi, I have a dodge neon and the engine light is on. The code came up as a p0420 i think, the description was

-catalytic converter

-engine misfire

-large vacuum leak

-engine oil leakage into exhast—valve guide seals, piston rings

I believe it’s the last one because I have oil in my driveway. What is the best way to figure this out other that taking it to amechanic? And how much of a problem is this? The car runs fine but I know I need to get it repaired ASAP. thank you



Good day to you Leann,

That code is going to have to do with the Catalytic converter system….either there is a problem and the converter needs to be replaced, there could be something wrong with the oxygen sensors causing the engine to run “rich” and use more fuel than needed, or there could be a misfire, like from a bad spark plug wire that is causing the engine to run rough and not burn all the fuel inside the engine…thus sending too much unburned fuel out the converter.

I would rule out, bad spark plugs and spark plug wires first! That is about the only simple thing you can do yourself. If the wires and plugs have more than 75K miles on them… MIGHT want to replace them as maintenance anyway…..and pray that also solves your other problem.

A muffler shop can test your converter for you, relatively cheaply. I would also get a mechanic to reset the light for you and see if it comes back on, there is a chance it might not…..unless the problem continues and your computer sees the problem again and sets the light to warn you about a problem. Things like this are just too complex without the proper tools and training.


Austin Davis

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Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."
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