peter_s

Okay so I just bought a used Honda Accord 2013 lx about a month ago, Had 48K miles and had my mechanic check it out and put a new inspection sticker and everything passed. Now about a month later the engine light comes on and the code that is coming back is P0420 Catalyst System Efficiency Below Threshold B1. I can't believe the Catalytic Converter is now failing all of a sudden. Especially since the inspection passed the catalytic converter. So a couple of questions. First is does anyone know know if Honda will cover this? There seems to be a 70k or 80k mile federal warranty. Second is that my daughter is driving this back to school from MA to PA and I am thinking np she can get that fixed at a dealer out there. She is leaving in a few days to go back and the dealers here are booked here. Does that seem like a reasonable course of action? Everything I read says you can drive it for a long time with that light as long as it is not blinking. Seems odd to me as it passed inspection and the car doesn't have much mileage on it. I made sure the gas cap was tight and going to see if in the next 50 miles before she leaves if the light goes off. Anyone heard of any problems with the Catalytic Converter and Honda Accords?

MAD_MIKE

State/region Inspections are just to make sure everything is in order and nothing is failed. It's not something you would use to judge the condition of your vehicle, as strange as that may seem. It's just to verify the car meets minimum on road safety requirements.

P0420 is NOT a code stating that the catalyst is failing, it is a code that states the System Efficiency Below Threshold. This just means that the catalyst is not able to keep the output emissions within expected parameters. Again this is not a catalyst fault issue. It's an efficiency issue of the emissions system in total, which includes the operational condition of the powertrain as well.
Most OBD code descriptions are anywhere from vague to useless. It just points you in the direction of the fault, not what the actual fault is.

If, after diagnostics, it is determined to be a fault in the system itself that is covered under warranty, then yes they will cover it. However there is still usually a diagnostic fee and whatever they will charge to look at the car to determine fault, usually refunding that cost after repair(if under warranty).
Emissions warranty is for five years, regardless of mileage. So make sure your still under that 5 year(after purchase) warranty.
Make sure to document the process as well, for your benefit.

Young woman dealing with mechanics is always bad ju-ju. Easiest of targets, especially if the car/person is not from the local area. Less likely to be given breaks and always given the worst possible scenario. If she does go make sure she is armed with the knowledge and facts about what the problem is, including the Emissions warranty knowledge, that is in the owners manual.

You can drive the vehicle, however without knowing exactly what is causing the fault the car may under perform or increase damage to the system that is affected. I wouldn't drive it normally, only if you have to.
Blinking is a currently happening fault. Solid light is a stored active hard fault. Light that comes on and then goes away is an intermittent fault.

Doubtful the catalyst is at fault. It is an efficiency code not a catalyst code. Hondas default code chucking is usually to set the P0420 before setting what may the actual problem be. A misfire code(P0300-P0306)will often come up after the P0420 code has already been set.

If you are capable of minor vehicle work you may find the fault yourself.
Verify the air filter is not plugged or heavily dust filled. Remove it, bang any loose dirt and do the light bulb check. If it hasn't been changed in 30Kmiles it is probably time you just did. Some oil changers may state and charge for a new filter but they may not actually change it.
Verify the MAF sensor is not coated in oil or soot. There may be security torx screws that will need to be removed to pull the sensor out of the housing. Using MAF sensor cleaner blast the internal sensors clean, you may need a flashlight to see them in the various passages. The main exposed bulb sensor should be a smooth amber color. If it has oil or junk on the end and covered in oil the sensor will become lazy or ineffective. Thoroughly spray out the internal passages and make sure the fluids drain out of the sensor. Cleaner will evaporate quickly, don't worry about it becoming trapped. Do not drop or hit the MAF sensor
Verify the coil on plugs are in good condition and the boots are not damaged. A faulty boot or corroded spring will cause a misfire issue.
Verify the spark plug wells are clean and dry. Any oil contamination may be an indication of a faulty valve cover gasket. Unless the oil looks new then a tech may have spilled oil onto the valve cover/coil plugs.
Verify the spark plugs are not loose nor are they worn out of spec. Replace with new plugs if they are out of spec.

More indepth would be to do a compression check and verify the valves are properly adjusted.
Honda usually states to check valve adjustment @ 90Kmiles, but it is best to check it every 30K miles as valve train can wear faster and need more frequent adjustment.

The above would cause a slight misfire which would then allow unburnt fuel to enter the exhaust system.
The catalyst is not designed to burn raw fuel but to catalyze existing toxic gases such as HCs, CO and NOx into non toxic CO2, H2O, and N.

Of course, none of this matters if the car has been going off road and high centering on the exhaust system. External physical damage is not covered under warranty.

peter_s

Okay I topped off her tank with (Shell) super unleaded and made sure the gas cap was tight and had her drive it for a while and the light went out. I am not sure what could have caused it. I am going to knock off as many of these great suggestions as I can. BTW, I did drive it myself while the light was on and it performed well. Gas mileage (through the dash screen) looked fine. I am not sure what else I can do at this point.