p0420 code while driving in the snow

Here (attached) is the P0420 code description. I have a hard time seeing how the brake / smell issues could have tripped this particular (cat) code.

I'm wondering if the burnt tire smell was actually from the catalytic converter and not the tires ... :thinking:

If i were to suspect that it was the catalytic converter, it would mostlikely be due to heat right? which i dont understand because the catalityc converters are bairly new, and the exhaust system is stock. Also, while i was up at 7000 ft, my engine coolant temp droped down to 174 degrees, i dont know if that had something to do with it? Also, could my tranny have been taking a beating since i have a tranny cooler, with about 25 degree weather outside and snow?

An exhaust leak could trip code P0420 - so it could have been as simple as a joint loosening under heat / cold stress.

If the engine cooled significantly, it could have been running inefficiently enough to trip the code. In other words, the code tripped because it 'thought' the converter efficiency had dropped (too much crud making it through into the exhaust), when in fact it might have just been transient blow-by from the engine.

There's also the outside chance that snow / moisture got to the heated (rear) O2 sensor and caused at least temporary oddball readings to get fed back to the ECM.

prepster said:

If i were to suspect that it was the catalytic converter, it would mostlikely be due to heat right? which i dont understand because the catalityc converters are bairly new, and the exhaust system is stock. Also, while i was up at 7000 ft, my engine coolant temp droped down to 174 degrees, i dont know if that had something to do with it? Also, could my tranny have been taking a beating since i have a tranny cooler, with about 25 degree weather outside and snow?

Click to expand...

Atmospheric pressure and altitude play a roll in emissions as your map/maf sensors give your ecu readings and fuel delivery specs. You can google this information to confirm or i can pm you with more details.

Billy
Honda Technician

I have the same code as well. I dont have a cat on my truck and ihavent for about 4 or 5 months and the code never came up. tomorrow iam going to put the cat back on and see what happens. Could it just be the o2s or the catnot being there any ideas? thanks

Reinstall the cat first to see if that clears it. If you ran the truck with no cat and both sensors still in place, it should have thrown a P0420 long ago.

The code gets thrown when the signal waveforms on the two sensors start changing at the same rate (i.e., when they signal differently it's good; when they signal similarly it's 'bad').

One or both sensors (and / or their circuits) may be 'dead'.