Fixmycar.pk highlights below some of the causes for p0420 Toyota Prius trouble code.
Oxygen Sensor – One can expect the code thrown when oxygen sensors on both sides of the exhaust display akin readings. The p0420 Toyota Prius trouble code can trigger when the oxygen sensor is bad and displays a false reading. If the engine does not display any of the decreased performance related with a bad catalytic converter. A bad oxygen sensor can also be a problem.
Catalytic Converter – It is the thing in hybrid auto that scrubs out as much pollution as possible from the Prius’s exhaust. With the passage of time it can become clogged. Although, today’s converters are supposed to last the life of most hybrid autos, still some problems can arise if converters are clogged.
O2 Sensor Wiring – Over time, the oxygen sensor wiring can get damaged. As it is prone due to the fact that it is right next to the hot exhaust at all times. The downstream oxygen sensor wiring is volatile too for being distant from the ECM. Thus a damaged O2 sensor wiring can cause p0420 Toyota Prius trouble code.
Prius Timing – If the exhaust timing is off of your Prius, this can affect the gasses that are actually going to the O2 sensors thus triggering code.
Exhaust Leak – In the case of an exhaust leak coming from the vehicle the O2 sensors also throw p0420 error code.
Engine Temp Sensor – If the software doesn’t figure what the engine temp is it’ll keep the fuel mixture rich causing the exhaust the O2 sensors see will be out of range and so forth p0420 Toyota Prius trouble code.