hypervish

Hey, guys/gals. Hope you all are doing well. I have a 97' Honda Accord with 205k miles on it, and I need to get it inspected sometime this month (with emissions). I'm getting two codes P0420 and P1457. Where should I start? I already tried replacing the gas cap.

phootbag

P0420 is set when the secondary oxygen sensor signal suggests the catalytic converter is no longer functioning sufficiently. It is highly unlikely that there is a sensor or wiring failure as the criteria for this DTC is such that the secondary oxygen sensor data must closely resemble the primary oxygen sensor data. This is hard to reproduce with a sensor or wiring fault. The problem is likely a contaminated catalytic converter. Replacement is necessary.

The P1457 is an EVAP DTC, as you are aware. However, this DTC is for the canister portion of the system rather than the fuel tank portion. A faulty fuel cap will not cause this DTC. The system complexity MAY require you pay a qualified technician to diagnose.

exb18c1

As a "PHOOTBAG" said you better go to garage,instead of changing parts for nothing.It's very often that the vent valve leaks (it rusts trough the body) and the worst thing that its almost impossible to unscrew it from the canister.(at least in places where there is winter).The qualified garage suppose to have a smoke machine,which introduces a smoke into EVAP system so you cantrack it down.

hypervish

Ok, thanks for the advice. I reset the codes yesterday, I'm waiting to see which one's come back, so I can start fixing them.

h0p3l355dork

Yeah, I had a P0420 on my 99 accord v6 and had to replace the cat for emissions too.. 500 dollars later i passed.

Roader

After resetting the ECU, my '96 will go a thousand miles before it throws a P0420 (67) catalyst system efficiency below threshold CEL, and it passes emissions easily. You might try resetting the ECU right before you go to get it inspected.

h0p3l355dork

Although that might work, be sure to drive it and make sure the "emissions ready" flag is set (after about 25-30 miles. Otherwise you fail emissions immediately. (Well I'm in California...) [And I speak from experience.. very embarrassing 30 dollar experience]

exb18c1

Yeah,now you have to pass through drive cycles to set the readiness monitors,otherwise they will know that you reset the trouble codes and they wont pass you.