Diagnostic codes 420 sienna Toyota ce what this codes mean and how to fix it?

Answer 1

This error code is most common on vehicles that spend much of their time at low speeds, on short trips, and doing city driving. It's possible that the catalytic converter in such cases rarely gets hot enough to help burn off contaminants, and those contaminants end up preventing the chemicals in the exhaust from reaching the catalyst element. A long, hard, highway drive may cook off enough of the contaminants that the cat may start working well enough again to turn off the light.

Drive at a time when you can get up to the highest speed limit that's legal in your area, and stay there for an hour or more. Add load to the engine by (all at the same time) turning on the A/C, the heater fan full-blast, the headlights, and open all the windows to increase drag. Sounds silly doesn't it? But doing all these things will make the engine work harder, which makes it use more fuel and thus better heat up the catalytic converter, which may help it cook off the crud that led to the error.