P0335 - what is the first thing that needs to be done to fix problem

Question

What would be the first thing to check on a 2005 Santa Fe SUV that has the 2 error codes P0335 and P0420.

Answer 1

P0335 most likely the crankshaft position sensor needs to be replaced.

For P0420 is the car has been maintained well and spark plugs and timing belt has been replaced (if it was needed) replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem