Hello, my CEL popped with a P0420 code, appearing to be a bad catalytic convertor. This was grandma's car ('02 L100), and it only has 17K miles. Can a catalytic converter go bad in 17K, or did age simply take its toll? Been getting normal use since I took ownership. Should I try a pour-in 'cleaning' product to see if can clear the code, or, are those liquids worthless? Any help appreciated before spending more money. Thank you.

 

DO NOT USE CLEANERS. How has it been running? Time doesn't kill a cat but misfires will.

 

I'd try changing the plugs and running a bottle of Techron Fuel System Cleaner through a tank of gas. I don't think it's related to the cat con. BUT, I'm not a mechanic with a garage like grcauto8453. Follow his advice because he knows his stuff.

 

The car runs absolutely perfect, smooth from idle through highway speeds. Ya, I can't believe the cat is spent at only 17K. I then thought maybe an O2 sensor might be the issue, but that typically throws a different code. What is the harm in using one of those cleaners, btw? Any other thoughts would be appreciated. Thank you.

 

It just passed emissions inspection last month, so should be no issues with that. Again, it starts and runs like a dream. Many years ago it got the Saturn recall for ignition coii pack replacement, so I assume plugs were swapped then. Thank you.

 

Is 0420 the only code you're getting?
What kind of MPG are you getting?

 

Correct, just that one code. Honestly, I have not checked gas mileage yet, I'm only on my third fill-up since buying it. It seems to be very economical. What are you thinking I should consider? I have a good master mechanic that could do a deep diagnostic test...but that's a $75 test.

 

The car should get 29-30 mpg mixed driving.

 

Have you checked the air filter and made sure it's in good condition? If it's running rich, it can throw that P0420. Also, how does the exhaust sound? If you have air leaks in the exhaust, that can throw that code too.

 

Both are fine. Im going to run a fuel system flush/ clean and see what happens. Doubt it ever had one in these last 23 years...who knows.