996 Catalytic converter issue

I have a 2001 996 and the CEL recently went on. I was told by the shop it is the catalytic converter and decided to replace it with a FabSpeed x-pipe. While the part is being delivered I have my car back and the CEL is no longer on. Does anybody have experience with how long it takes for it to come back on after being reset? I've driven the car about 10 miles. Is it possible the shop made a mistake with the diag? I live in Chicago. If people in this area can recommend a mechanic they trust I would appreciate it. Given this is an expensive operation (not to mention the change in sound) a second opinion would be useful.

Could be 11 miles, could be 11,000 miles. Only one way to find out.

My experience is that it can be very random. Sometimes after a few days the CEL will come back, sometimes after a month or more.

I would assume the shop reset the light while it was in there and if the catalyst is bad, the CEL will certainly come back on once it fails a drive cycle. That being said, replacement converters are only about $250 ish.

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Depends. BTW, do you know the error code? My 2002 Boxster would generate a P0430 error code. It would appear every so often but with enough time between appearances I could only recall it had appeared before but I couldn't recall when. (I never bothered to log these codes. Part of me didn't want to know...) It was weeks to months between appearances with the more frequent appearances happening in the winter months while during the summer I recall seeing it very infrequently if at all. It appeared even less frequently when I switched from discount gasoline to Shell gasoline. I can tell you 10 miles is probably not enough time for the DME to trigger the error code unless the failure is pretty solid. A good way to try to get the error code to appear is to take car out on a drive cycle, a drive cycle intended to help the DME go through all its readiness monitor tests. During this drive cycle the DME will test various systems/sub-systems and at some point it will set all the readiness monitors to complete. If it can't set a monitor to complete odds are it will be set an active error code and turn on the CEL. Maybe. Depending on various factors it may not set an active code but instead set a pending code.

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Same for me. Usually within a few weeks. Sometimes I can drive around town for weeks and then one highway drive will activate it.

Macster, I don't have the error code, just relying on what the shop told me. I will get an ODB reader (unfortunately it has become more an more necessary despite the car having only 50K) to check for pending codes as well. Thanks for the advice everybody. This weekend I will do more driving with friends visiting so will see what happens.

Gonna throw my $0.02 in. I have an '03 C2 Tip w 135k miles. I bought the car 3 years ago at 108k mi without any issues. In the 2nd year at the 115k mark, the P0430 CEL came on. Catalytic below efficiency - Bank 2 (Passenger). Ignored this, cleared the light. About 6 months at around 120k, CEL lit up again. As time went on, the frequency of the light became more common. After clearing, 1000 miles, 500 miles, 120 miles, now anywhere from 25 miles to 60 miles the CEL would light. Reason is the CAT has a brick of precious metals like Platinum and stuff to scrub off the hydrocarbons and nitrogen oxide. After multiple heating cycles (13 years), the platinum wears away. I heard 75% left of platinum is all it takes to trigger the CEL. So you can clear it like me but it will eventually come back. Since I'm in California, smoging the car is an issue so I did what everyone said to do and swap out the O2 sensors from each side (instead of buying new ones) to see if it's a bad O2 plug. No difference. P0430 comes back. Time to order a new CAT. I've got quotes from $400 for a used CAT (a 10 year old CAT for $400?!?) to $2000 from Pelican. So I went to my goto muffler welder guy in Poway, CA and asked if he could just weld in an aftermarket unit that was a Universal 200 cell CAT in place. He said sorry bud, CA is really strict with their aftermarket CAT replacement and said stock was the way to go. I'm not going to pay $2000 for one CAT so he directed me to the Air Resource Board website. On the website, it shows available aftermarket CATs (Magnaflow, Valina, and Walker MFG) you can plug into your car legally in CA. You actually have to match the engine family (code for US emissions) with the available vendors and part numbers. So I picked Magnaflow for around $500 with shipping and it's arriving in a week. That said... wish me luck!

Just as an FYI, you may still get occasional CEL even with a brand new Fabspeed's.

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No luck needed! As you already know, the Magnaflows are a direct fit /bolt-on and will pass visual/sniff testing. Yes, I have them on my car and zero problems. P.S. Per Magnaflow warranty requirements...install must be done by a shop (no DIY) who signs paperwork which you mail in with your sales receipt.

It seems my situation is similar to yours, drew996. I've driven a good amount since my last post and no CEL. Wish I had asked the question here before committing to the Fabspeed, probably could have waited. The shop did not say anything either, surprise surprise. The only reason I got the car back was that no Fabspeed units were available for a couple of week. Hopefully I like the Fabespeed sound... The shop guarantees the work for 3 years so the CEL coming back on won't be an issue, at least not for a while. These toys are not cheap to maintain once they age, are they?