P0420 i believe is a catalytic convertor efficiency code. if the cat has gone bad, it should be under warranty (emissions items have a very different, government enforced warranty period).
You need a new Catalytic Converter
SOURCE: I have a 2001 chevy S-10 2.2 liter. What does Code P0420 mean??
here are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly.
The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.
The easiest thing to do first is a visual check of things. Visually inspect the exhaust system for leaks, check the catalytic converter for dents, holes, severe discoloration, and check for a rattle inside. If any of those syptoms are there, the converter likely needs replacement.
Then, visually inspect the downstream O2 sensor (behind the converter). Check for broken wires, obvious faults, etc. If all that checks out, you'll want to check the operation of the O2 sensor. To do that, you'll need access to a scan tool or oscilliscope. Check that the waveform is pretty steady. If the reading fluctuates then the sensor is likely bad and will need to be replaced.
Try this, turn the ignition key to the on position, (engine not running) and pull the fuse to your ECM for 30 seconds and then re-install it. Once re-installed, start the engine and let idle for 1 min and then go for a test drive.
If the engine stalls, let it. The ECM is relearning the sensors and engine, just restart it and after 1 min when the RPM drops. God for a test drive and see if the service engine light comes back on and re-scan for the DTC codes and address the issues indicated by the DTC code.
Thank you for using fixya and good luck.
SOURCE: P0420 & P0430 codes 99 silverado
codes p0420 and p0430 are both post o2 sensors, the ones after the convertor, both sides if replacing
SOURCE: 2001 golf gti had fault
re the funny smell, i need to speak to my friend as i have never heard of that one,does it smell of rotten eggs???
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take it to a dealer and have the vapor recovery system leak tested.
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