2001 Boxster 40k miles with PO 420 and PO 430 codes

Hi, I just bought a boxster from a dealer 200 miles away. The car runs great but on the way home the CEL light came on. It is giving me po420 and po430 codes. I ordered new spark plugs, air filter, and 4 new 02 sensors. I called the dealer and they told me the 02 sensor must of timed out. I have not heard of a sensor timing out and needed some advice. Should I use Seafoam or Techron on a regular basis? Oh and I bought a 3 month 3k mile warranty that I'm hoping will cover a new cat if that's what the issue is. Any advice would be great!

Adam

When I clear the CEL light it will stay off for about 100 miles and then comes back on.

P0420 is Catalyst Efficiency Below Threshold (Bank 1)
P0430 is Catalyst Efficiency Below Threshold (Bank 2)

error code diagnostic guidelines read that if one/both of these codes appear if accompanied by any O2 sensor aging codes to replace the sensors indicated by the codes, clear the codes, then drive the car to ensure the converters aren't also bad.

You've replaced the plugs, sensors, so I'd say if the codes come back in 100 miles of driving -- and they do -- the converters are toast.

I'm reluctant to add this but to be thorough...

As I've mentioned before my 02 Boxster generates a P0430 and there are no O2 sensor codes. I have found a couple of things that affect the frequency at which this code appears.

Running 'supermarket' gas station gasoline, even though it is 91 (all I can get out here in CA) octane appears to cause the converter to act up some.

(Oh, might add there that by act up the codes essentially mean the indicated converter can't store oxygen which it must so it can process exhaust gases.)

Anyhow, just one or two tanks is enough. And it takes a tank or two of the 'good stuff' (for me Shell V-Power because a Shell station is handy to my house and offers competitive prices to other stations (Chevron, 76) in the area.

Cold weather. I can't do anything about that and neither can you but I have observed the code is more likely to appear when colder weather is upon where I live and drive and this no matter which gas I fill the tank with or how I drive the car.

Lastly, short trips seem to make the error code appear more readily.

Lately I've been really driving the car -- running sometimes over 100 miles per day mostly at highway speeds -- and the CEL has not come on since we had a spell of cold/wet weather here and that's been awhile. All this driving has another benefit: The engine's just purring. Admittedly, it has been rather unseasonably warm but not in the mornings when I'm out and about. Often I have to wait for the car to warm up some to defrost the ice on the windshield.

My advice though is don't try to find a way to nurse those sick converters to some kind of good health -- which will be temporary and short-lived at that -- but instead use that warranty quick to get them replaced.

*Then* follow or try to follow good converter hygiene to prolong the life of the new converters.

Don't delay on that warranty: Last time I checked and it has been over a year ago and prices have only gone up a factory converter from a dealer (which means the thing comes with a 2 year warranty) is over $1000 and the labor to remove the old one (I'm told very often when the old one is removed a bolt snaps and the tech has to take extra time to remove the broken bolt so often the extra labor added in vs. trying to get permission after the fact from the owner of the car) and install the new one adds another 2 hours or thereabouts. In my area labor is $150/hour.

Sincerely,

MarcW.

Are you sure you have the right O2 sensors for the ECU you have? That codes show up on both sides makes me think it is something common or something shared. Did you order the ones with factory crimped pigtails?

I ordered the direct fit sensors instead of the ones you crimp. I'm in Indiana and it is cold here. The car runs great still. I'll have them checked out cause the warranty is up in May. The dealer had mentioned that the sales guy put 89 octane in the car instead of premium gas. I reset the code and drove the car 180 miles and it hasn't came back on yet.

Thank you,
Adam

I haven;t installed the new plugs or sensors yet. They actually just arrived today. Thanks for all the help! I'll have them installed and see what happens.