Code P0420 I have a 01 honda accord ex 2.3 liter v tech engine wich has california emissions. My check engine light is on. it had failed inspection so i did a complete tune-up , oil change, air filter,. I replaced the knock sensor because there was a code for it and it was actually broken. and i also changed the egr sensor because there was a code for that and it was clogged. my check engine light went off and when i got to the inspection station it came back on on and now i am showing P0420. can anyone help.

Look at this information and don't ever over fill the car as it can push fuel into the emissions canister and cause problems.
http://honda-tech.com/honda-accord-1990-2002-2/98-accord-problem-code-p1456-2460060/

You likely have a failed transmission, have a shop confirm this.

Engine light comes on when a particular part is under-performing, not necessarily broken. Have the vehicle scanned, and find out which part is the culprit. For example, a oxygen sensor not working right will light up the engine light, it will not affect performance, but the vehicle will not pass emissions inspection.

that is the sensor that is behind the catalytic converter, it just measures effiicency of the cat itself-the sensor has a wire that pre-heats the sensor so that it goes 'on line' sooner, it has failed or is failing-the easiest thing to do is replace the O2 sensor, or you could ignore it until you have to go through emissions, and replace it a few days prior to inspection-but if you do that, and something else malfunctions that your check engine light would warn you about, you wouldn't know it-so it's probably just best to replace it when you can, in the near future. It will not affect at all how the car runs though.

Even if you reset it you will still fail the test because the emissions monitor testing will not be complete. Once the monitors are complete the check engine light will turn on because the cat is bad. Its a catch 22.

If its just a safety inspection you may be able to get away with resetting the light. You can try disconnecting the battery for about a minute. or you can remove the back-up radio(clock) fuse from the under hood fuse block for about 30 seconds.

If you live in the continental US and your catalytic converter is bad your vehicle is not eligible to be licensed for on road use per Federal Emissions Laws.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

either reset the computer or get a diagnostic scan to find the problem. the check engine light on doesn't mean it won't pass inspection

there is also an egr control solenoid in the ciurcuit. either vacuum controled or electriclly controled

The only thing I can think of checking would be the EGR valve, a faulty cat converter or faulty o2 sensor. Converter shouldn't set off check engine light though unless it is clogged causing too much back pressure, most likely EGR Valve.

how many liters is the engine on 92 honda accord ex? when i get up to about 45mph or somtimes 60mph the car jerks and then after that the check engine light comes on what could be the problem?