Heat

'99 Accord LX. Four cylinder engine, about 117,000 miles. Original exaust system (including original cat).

It runs just fine, not sluggish or anything.

The check engine light came on a couple of months ago, I had the code checked and the guy at Autozone said it was something with the catalytic converter (probably the P0420 code), and to replace the spark plugs. So I did. The light went away a few days later and came back a few weeks ago. It's now reading P1457 and P0420.

Per Autozone:

P1457: EVAP emission control system leak detected (control canister system)

Probable cause:
1. Loose fuel cap (I always click my gas cap at least three times)
2. Vapor caniser saturated
3. Failed vent solenoid
4. Failed purge solenoid

P0420: Catalyst system efficiency below threshold bank 1

Probable cause:
1. A/F ratio concern
2. Air leak near H02S (Heated oxygen sensor) Bank 1
3. Ignition system concern
4. Faulty catalytic converter

So... what's the most likely cause?

Thanks!

kijunglee1234

for p1457:
i went to a junkyard and pocketed an evap canister vent solenoid, replaced and went away. that was MY solution. best way to find the problem is to smoke test the fuel system. i would:
depressurize the fuel system by pulling the fuel pump fuse, and starting the car until it dies. i do it twice more for good measure. then, from the fuel pressure regulator i would plug in the smoke machine from the f.p.r. towards the tank, not towards the injectors. wait a minute or so till the smoke can fill the system and go under and look for smoke. note that fuel will spill where you unplug lines And the vent solenoid vents into the box frame closest to the canister. if you see smoke coming from the frame, thats your problem.
As for p0420? i still have that along with a lean code. i believe p0157?(cannot recall)
TAP the cat with a soft mallet hammer and listen for dust falling(in the catalytic converter) if so, you have a failed cat but because you dont hear anything doesnt mean nothing is wrong just the only test you can do and would be an obvious answer. you can hook up a digital oscilloscope to the o2 sensors and see if either o2 is lagging. if like me you are trying to bring the car back to stock because the previous owner couldn't care for an automobile, then i would suggest replacing the plugs, wires, distributor, pcv, egr, f.p.r., timing belt, pulleys, water pump, oil, oil filter, etc.
i'm probably forgetting something but that is the jist. good luck if you need help. pm me at kijunglee1234@gmail.com