Q: Check Engine Light P0420 trouble code

asked by on November 10, 2016

i have 2011 nissan altima. About a month ago the CES light came on and was on for about two weeks. I just purchased a new transmission less than 5 months ago so I thought there may be an issue with it. It took it back to the dealership immediately. They ran a diagnostic check on it and informed me that the error code is PO420, and that I may be able to get it repaired cheaper at a muffler shop. However, I have not had the income to get it repaired yet. A week later the CES light went off by itself. Now, three weeks later it has come on again. Could something other than the catalytic converter be causing the CES light to come on?

My car has 138000 miles.
My car has an automatic transmission.

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Hi there, thanks for writing in. Typically, a P0420 code (catalyst efficiency insufficient) is the catalytic converter not properly functioning. Chances are, the Check Engine Light going off and then back on, it’s still the P0420 code that is present. An exhaust leak(s) and rarely O2 sensor faults, can also cause this code to set. To avoid any unnecessary repairs, I recommend having your vehicle’s P0420 trouble code be diagnosed and repaired by a certified technician, such as one from YourMechanic.

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