Engine light: P0420 Powertrain Catalyst

[jrvibepalmsprings]

Hello and thank you to the genvibe community. I had the check engine light on, which gave a code of P0420, the powertrain catalyst system. I have a 2003 vibe, and was hoping I didn't need a new catalytic converter.

So I read some posts on genvibe and decided to follow the advice of fixing inexpensive things first. I replaced the air filter and spark plugs to no effect (but mpg improved). So I changed both oxygen sensors, and that did the trick. So thank you genvibers, you saved me from having to buy a very expensive catalytic converter......

[ken99287]

Changing the o2 sensors may just be a temporary fix for a failing cat.

Do a search for "p0420 defouler".

[vibrologist]

Another temporary respite can be gained with LACQUER THINNER (not paint thinner!).

http://www.youtube.com/watch?v=5icTmYItwiE" onclick="window.open(this.href);return false;

[Derf]

I did try the lacquer thinner first (cheap fix), was not my issue, turned out to be bad (cheap non-oem previous replacement) post cat sensor. If you do try the lacquer thinner, plan a long trip to burn the fuel/lacquer blend down as much as possible. The lacquer thinner can cause certain fuel system rubber o-rings/seals to swell. Burning the tank up quickly reduces this issue.

[jrvibepalmsprings]

Thanks for the info about the defouler. I might try that if the engine light comes back on. If my cat is going bad, how long would it take for the engine light to reappear? Its been 2 weeks since I changed the oxygen sensors and the light has stayed off. Thanks for the help!

[lannvouivre]

Thanks for the info about the defouler. I might try that if the engine light comes back on. If my cat is going bad, how long would it take for the engine light to reappear? Its been 2 weeks since I changed the oxygen sensors and the light has stayed off. Thanks for the help!

You only need to wait for the temperature of the O2 sensor to get high enough for a proper reading, so long enough to get to operating temperature. Worst case scenario if your cat is still good is if it's dirty enough not to flow well.

[Reaccion]

Take a look at this thread:

viewtopic.php?f=12&t=39506" onclick="window.open(this.href);return false;

[ken99287]

2 defoulers are $4 at advance, I believe. Drill the first one out so the tip of the O2 sensor will just fit. Then screw it onto the O2 sensor. Then screw the other unmodified defouler on. Then reinstall into the exhaust.

This will cause the rear O2 to artificially read "cleaner" than it should. If the p0420 stays off, your problem is bad CAT. If the code comes back, the CAT may or may not be bad, but you've got something else going on too, likely one or both O2 sensors.

Even though this could keep the p0420 from coming back for quite some time(sometimes years, I've read), don't forget to replace your CAT asap, as this method is just a test, not a solution.