Learn More About Code p0420

Code p0420 is a code that your cars computer will set when it sees that the catalytic converter is not working efficiently. This can be either because the CAT (Catalytic Converter) is not working properly, but it is more often set because of something besides the CAT. Here are the most likely causes of this code:

Engine Misfire
High Engine Oil or Coolant Consumption (Being burned in the cylinders)
Rich or Lean Fuel Mixture
Oxygen Sensor

Other things that can cause this code:

Retarded Spark Timing
Leaded Gasoline Used
Leaking Exhaust System
Malfunctioning CAT
Weak or Poor Spark
Coolant Temperature Sensor

The first thing to do when trying to diagnose this code is to diagnose any other code that might be present. It is unlikely that this code will be set by itself.

If there are no other codes then the first things to check are your engine oil and coolant levels (if they are low it indicates that they are either leaking externally or being burned in the engine). The next most common thing to check/replace if there are not other engine codes is the Oxygen Sensors. If they are not working properly they can cause this type of code.



Leave p0420 and go back to OBD codes