I have a code reading of P0420 for a Saturn - Lseries. What can be the problem?

Question

I just took my daughter's first car for inspection and it failed. It had a PO420 code readong for the 2001 Saturn LSeries. Any idea of what the problem may be?

Answer 1

P0420 is usually for a bad catalytic converter which can be the cause in the long run of using low octane fuel. Most likely the catalytic converter is bad. You can try to do an intake flush and use 91 octane from shell. 

Also drive the car a little hard to get the catalytic converter hot enough to burn all the carbon build up out