What code po420 means and what you need to do service engine soon light on and this code came up on scan ty for info?

It means your oxygen sensor in your catalytic converter is reporting that your catalytic converter is bad. You either need to replace the sensor, replace the catalytic converter or clean the catalytic converter if you're broke. You can test your catalytic converter by drilling a small hole on the tailpipe before the catalytic converter and after the catalytic converter. Have a friend rev the engine to 2000rpm and feel the amount of air coming from both holes. If they feel drastically different then you know your catalytic converter is clogged. If they feel the same then change your O2 sensor. Disconnect the negative side of your battery and it will make the check engine light go off.



The above answer is somewhat off. PO420 means Catalyst System Efficiency Below Threshold (bank 1). It can be a defective catalytic converter or bad O2 sensor but may not be. Don't go throwing parts at the problem or you may spend lots of money and still have the problem. It can be either of these problems but it can also be an exhaust leak, damaged exhaust pipe, wiring at the O2 sensor is loose, corroded, or damage. Can also be the converter is actually clogged. My advice is to have this repaired by a professional who knows what they are doing. Converters are very expensive and unless this car has been neglected or damaged then the converter should not be bad. Know that the converter has a much longer warranty that the rest of the car. Check to see if it is still under warranty.