Hey Scotty, greetings from the Republic of Georgia. I recently bought a Ford Focus 2013 SE Hatchback…


Hey Scotty, greetings from the Republic of Georgia. I recently bought a Ford Focus 2013 SE Hatchback 4D, 4-Cyl, Flex fuel, 2.0L, with automatic transmission and mileage of 98,000 miles (imported after buying from copart auction with no serious damage, only minor dents and scratches). I love the car, it runs great, but has a check engine light on due to code P0420.

I decided to check the O2 sensors voltage, but I could not retrieve data from sensor 1, whereas sensor 2 showed the following: while idling on hot voltage stays between 0.7 and 0.8 for about 30 seconds, then goes down to 0.1 and up again, and does this repeatedly with intervals of about 30 second. It also goes down and up while pressing gas pedal, stays almost constant between 0.6 and 0.8 while revving at about 2000 rpm and goes down and up when releasing the gas pedal. Does this data represent a bad catalytic converter?

Also, I am getting quite high gas mileage - about 4.6 gallons per 100 miles. Well, in my country we do not have roads as good as in the US, but I know some people here who get comparatively low - about 3.4 gallons per 100 miles on the same cars.

What would you recommend to do next? Should I try to clean the cat? (If yes, please recommend how to do it - e.g. using Lacquer Thinner/Cataclean or just soap and water overnight etc.) Do I have to replace O2 sensor/cat itself? Or maybe I should implement some more tests to find a problem?

Thanks in advance for response! Best regards from the Republic of Georgia!

Comments (2)
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Scotty Kilmer
Scotty Kilmer


one, those are crapper cars at that mileage, cat is probably shot but it is so because of underlying problems clogging it up. That fuel and ignition system is so complex on that model, find a pro to work on it, or ditch it and get a better vehicle. They often turn into money pits.