Q: P0421 and P0401 codes have appeared

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I took my car to get it diagnosed and the codes p0421 and p0401 popped up... can I know what is... is it something to be concerned? And which one should I take care of first... they told me that it'll come out to 700.00 to get it repaired

My car has 219000 miles.
My car has an automatic transmission.

Hello. The codes P0421 and P0401 refer to the oxygen sensor and EGR valve, respectively. It is possible that an issue with one is causing the fault to be seen by the other, as they will work loosely together. It would be best to have a certified technician perform diagnostics on the codes to pinpoint the problem. They can hook a scanner up to the vehicle and read the actual data from the components, and this will show them where they will need to look for the fault.

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