your opinions/ experience? 06 Cayman S CEL P0421. car only has 7800 on odo

Hi folks, New to the forum. Sorry if I'm in the wrong place. Need some advice. Just bought a ' 06 Cayman S . Only 7,800 miles on it. Manual trans. Two days after buying it (and driving it on a 3 hour 70mph+ drive to get it home), the CEL came on. Friend at the local dealership pulled code and it was a P0421 ("Warm up catalyst efficiency below threshold bank 1 below limit value), said I should just drive it hard to clear it out. He cleared the code, but two days and 30 miles later, CEL came back on. Seems to run ok. I had an 06 CS a couple of years ago and this current one seems to run with just a slightly rougher idle. May seem a little more sluggish...but could be my imagination. Nothing significant that I can tell. I can't imagine the Cat would be bad....the thing has hardly done anything throughout its life. I have seen it mentioned that I could do a Softronic flash, but I live in a county with emissions testing. Not sure if that would be a problem (I haven't gone through emissions yet to get a license plate for it... OR is there any other option you would recommend? I grew up in a muscle car family doing minor stuff here and there, but I am absolutely clueless when it comes to cars with any modern tech. Can probably do some reasonably simple stuff myself. Thanks in advance for any assistance or advice you guys may have for me, and I look forward to checking this site/forum out often. Mike

I had that recently on my ‘06 CS with about 70k miles. I track it heavily. My tech said that it was likely just burning some oil off. I’ve had issues with the Air Oil Separator. Do you have smoke at startup? I always run it hard and haven’t had the CEL come back on since that one time. Sent from my iPhone using Tapatalk

Have not seen any smoke at start up, or at any point. I have seen other 987s start up and have seen substantial smoke. Also the previous owner was definitely NOT an aggressive driver, it appears. I have been pretty mellow with it as well. A bit more aggressive since I was told to 'clear it out.'

I'd say it's either your driver side cat or the aft 02 sensor.

I agree with your mechanic. My previous Boxster ( 987.1 S) felt pretty sluggish for two months after I bought it, but I just chalked it up to me being picky bastard. Then I went out for an autocross day and ran the course probably ten times. The very next day, I could feel the difference. It felt like a whole new car, throttle was quicker, acceleration was sharper, etc.... My mechanic said that because the car had been sitting for so long before I bought it that the engine and internals were gummed up and sticky from lack of use, but you have to really work the engine to get the combustion chamber and exhaust hot enough to burn it all out. Think of grandma's cast iron pans. All that great built-up seasoning is polymerized oil that has been cooked onto the metal. Normal use will just keep adding to the build up. But get those pans super hot for a while and that residue will burn off. Bad for grandma's cast iron pans but good for your engine. And good for the catalytic converter if it does have any build up. So take the CS for a hardcore drive or autocross or full-on track day, anything that will get the engine working really hard and hot.

You might consider adding a bottle of a good fuel injector/fuel system cleaner the next time you gas up.

Does it have any exhaust or headers modifications?

I like your analogy! I get it. That does make sense. Good excuse to have some fun.

Just added some this afternoon. Taking it to work tomorrow. Will get a chance to open it up a bit and let the cleaner do its thing.

No mods. Completely stock. But if it comes down to having to replace the cats, I'm probably going to look into some different exhaust / headers .

I have just thrown the same codes with P0421 and 22; bank 1 & 2 after cat O2 sensors . Carnewal exhaust mod and OFT flash for more than 50,000 miles. I am burning more oil and have smoke more often at start. I do not baby my car but also have not had a track day in more than a year. 91,000+ miles on my ‘06. Never seen a code on the car in over 4 years of ownership nor since the minor exhaust mod. First codes thrown about two weeks ago. I cleared the codes and stayed clear for about 2 days. Just came back on. Car does seem to idle a bit more rough but not that noticeably rougher. I was going to get on scanner to measure voltage on the sensors to diagnose if faulty sensor or possible bad cats. This is the first I have read about driving hard to clear.

I am with your mechanic on this as a start. Put fresh gas in it, put in some liqui moly injector cleaner and take it for a ride, but a real one. I don't mean anything crazy but as the car was meant to be driven. '06 with 7800 mi. - this car has not done anything in its life yet. It is a baby! If that does not help then you may start looking at O2 sensors although with such a low mileage I doubt it.

I had a similar issue with my 06 Cayman S . Happened after I got some gas at an out of the way station. Local mechanic wanted to replace one of the cats, tho 02 sensor might have also caused the fault. But then the light went off and stayed off for the next 6 months I had the car... So don't do any repairs to quickly, at least not until you've done the "Italian tune up" as recommended above.

Threw a bottle of Cataclean in and have been driving the heck out of it. Keeping the rpm higher, trying to get it and keep it hot. So far, no changes. Light still on. Only driven about 200 miles with that tank of gas. Will wipe out this tank and get my buddy to clear the code again. See what happens. If that doesn't work, will talk to Softronic to see if their flash will get me through emissions. After that...whatever. May try O2. If no luck. May go for new exhaust . I have a way to contact both the regional Porsche service and the sales reps. See if I can get them to help out and cover under the previous warranty. Obviously the previous owner never drove it enough to even find out that this was an issue. Will keep posted. Thanks!

Keep in mind once the condition causing the CEL has stopped it will take a few drive cycles for CEL to turn off and the code will still be logged. You might want to get an inexpensive scan tool to clear the code with.

I am certainly a believer that we should expect our P-cars to last forever, but, in reality, this car is likely thirteen years old and has been driven an average of 600 miles a year. Is it really all that surprising that some of the components are doing something squirrelly? Sent from my iPad using Tapatalk