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My son has a 2000 civic 2dr. coupe its stock with 99,000 miles on it . it has been plagued with the p1457 evap canister code which we are still trying to find the cause . I have tested the system as per alldata which showed the canister shut valve was bad so I replaced it , it still throws the p1457 code. yesterday when I ran a scan it also showed the p0420 code so i ran a live test on the o2b1s1 and the osb1s2 sensors as you did in your cat test video. With the car up to temp and at Idle the o2b1s1 fluctuated as it should and the o2b1s2 held fairly steady between .5-.7 but when I raised the rpms to 2000 the o2b1s2 becomes erratic like the o2b1s1 is and when it returns to idle the o2b1s2 returns to a consistent .5-.7 again. I have not been able to do the cat. temp test yet. Does this indicate a bad cat. converter, or a bad o2b1s2 sensor. I did clear that code the other day and it has not returned yet and does not show as pending either. What are your thoughts?
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I’m afraid your cat is going bad. Your B2S2 behavior proves it, but in practice a cat code always means a bad cat. I have never in my career seen a cat code be caused by anything other than a bad cat.
Most mechanics will acknowledge cat codes are some of the only ones that you don’t actually need to diagnose, just throw the absurdly expensive part at it and it’s fixed.
About the code not coming back yet, it may be just because yours is still on the fringe. If it was outright failed, your S1 and S2 data would look identical at all times, even idle. Also, the catalyst monitor does not always run every time the car is driven because it has a few conditions that have to be met for it to run. If the drive doesn’t produce those conditions, the monitor doesn’t run (just like EVAP, EGR, and o2).
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