Check engine light came on, have a few questions.

Hey guys, after a spirited drive in the countryside, I decided to park my Cayman in the garage for the evening. After some cooling down time, I went to town to get some dinner instead. On the way back, during normal driving, the check engine light came on and the info screen said I should visit the workshop. I checked the gas cap , and it was snug, the car runs fine as far as I can tell. I'm wondering if I should go to an O'Reilly's or someplace with an OBDII scanner and have this checked, or will I have to take this to a Porsche specialist to read the codes? I'm hoping this isn't something serious.

Parts store can pull OBD2 codes. I'd start there, its free.:cheers:

+1. I believe the parts store can pull some of the codes but not all with a generic OBD reader, so it's worth a start there.

Very nice, This will hopefully be something minor. I'll keep You guys posted.

Well, just had it scanned at O'Reillys, and the code P0421 came up. If I recall this is an emission system code, either a Cat failure, or something similar. I was going to take it to a repair shop with a Porsche scan tool to maybe nail down the exact issue. My cats are covered until Jan. 2016, so if its indeed a cat failure, it can get replaced with little or no cost to me. Any other ideas guys?

Most likely and especially if you are not hearing rattling from Cat, it is your oxygen sensor. Also probably it is an aged oxygen sensor , the one behind catalytic converter . Try swap the oxygen sensor before CAT to one after CAT and see if the fault disappears -- if it does, then the aft CAT sensor is defective., which is my guess. Also check wiring as these sensors are low to the ground. Hope this helps. Mark

Ah ok, the car sounds normal, no rattling that I can hear. I'm wondering if a spirited drive could have been just enough to cause the sensor to fail, considering the length of the drive, and the time the engine spent in the 4000-6000rpm range. I think I got around 12-14mpg for the trip hehe. Oh, and the exhaust doesn't smell at all, if I remember, a bad cat will also make the exhaust smell bad.

It could be the wiring as I indicated earlier as it hangs too low to the ground. If the oxygen sensor is bad you won't necessarily smell bad odors from the exhaust , but smell test is not always accurate way to diagnose the issue. The oxygen sensor swap is easy enough to do and can quickly tell you if you have a bad sensor. Mark

Yeah, I'll check that first, should be easy enough. Thanks for the help!

Well, after some checking, I'm 99% certain its a bad cat. From what I've learned from the Porsche Dealership and from everything I've researched, its covered under the federal emissions warranty. So I shouldn't have to pay for at least the cat. The check engine light was cleared and it hasn't come back on since, but it did store the same code after a short drive. if it comes back on, I'll schedule a trip to the dealership to get the cat replaced.

I have had the check engine light come on with several different cars I have owned. The most common cause, and the cause that I have found in each of my cases was the gas cap seal. What I have done, is to lubricate the seal with something slippery.....I like "back to black". Dry it off. Then use something to clean the fill pipe where the cap attaches....I use some of the "back to black" again, then clean it off. Make sure the cap is on tight. It has always been the case that it will take a few re-starts for the check engine light to go out on its own.....assuming this was the solution. If this does the trick, problem solved. Sometimes I have done this and it is ok for awhile, then had to replace the gas gap as the seal had worn. Worth a try.

Just an update - The light hasn't came back on. I'm thinking it was either a fluke, or maybe my Cat is just on the threshold of setting off the CEL, and my spirited drive was just enough to set it off.. I remember hearing the early 06 CS had smaller cell count cats + a more sensitive parameter set for the O2 sensors . Please correct me if I'm wrong.

Well, just an update: I swapped the O2 sensors , and the CEL came on again on the same Bank. I'm guessing this will most likely mean a new Cat is in order. Any thoughts?

Hi, I have a bad cat on my 06 S and and my CEL comes and goes for the last 5 months or so, completely random. My local shop isolated the problem to the left bank. Unfortunately, my exhaust is out of warranty so I am looking at replacing the cats before my next emission testing. I live in CA and believe I have no other option than replacing the stock exhaust system because it will reportedly fail the visual portion of the emissions exam otherwise. Best of luck with your warranty replacement!

Had a similar problem and CEL code. My dealer suggested the following in this order: 1) Run BG 44K through the system. He said it might just be some carbon build up, and this stuff can usually fix the problem. 2) Replace O2 sensor 3) Possibly need a new cat, but they would need to do more than the 5 min diagnostic (i just dropped by the shop on the same drive my CEL popped on) So I tried the BG44K.... $20/can is pricey, but it worked. Pour it in just before filling the fuel tank, but then drive off that whole tank of gas within a 48hr window. I guess 44K doesn't work as well if you just let it sit in your tank. I had a long drive coming up that weekend and gave it a shot. CEL gradually went away. It came back a couple times throughout the month, but after 3 tanks of gas (only used BG44k on first tank), CEL is completely gone. I have the O2 sensors just in case, but so far, they aren't needed. Hope you can get your issue sorted out.

FYI, if the oil cap is not on tight it will throw a CEL also. Yes, I've also read that the 06's have tighter parameters. Here is another thread. http://www.planet-9.com/987-cayman-...oxster-problems-and-complaints/58858-check-light-again-catalyst-efficiency.html

I'm in the same boat. '06 CS. Luckily I dont have to smog mine until Aug 2017 but the light staying on is pissing me off. Do you know where you will get the replacement done at? Im in SoCal.

I followed the BG 44K recipe posted by bass 1 and my CEL has been off for 3 tanks of gas since! I am up for smog now and will be attempting passage early next month. Will try to remember to report back with results. My local shop is relatively small and in the central coast of california. The mechanic I trust gets invited to wrench for private teams racing Nurenburg(sp?) Ring and a friend, so I trust his advice. he advised cat replacement vs a trial of of modifying the post-cat 02 sensor. Theory being that lifting the distal 02 sensor 360* higher than the proximal with a spacer would allow for slightly cleaner emissions sampling at the post-cat sensor. in other words, artificially make the " exhaust " that the post-cat 02 sensor is sampling slightly contaminated with normal air. Thus, the post-cat 02 sensor always "samples" cleaner exhaust than the pre-cat sensor, so no CEL light. Hope this helps!

It's been a couple of tanks of gas since my last post. The CEL light has yet to illuminate since the BG 44K addition to the gas tank. My mechanic interrogated the car's computer this morning and says there is still a detectable error code coming from the left cat bank. He thought it would be worth trying to get it past emissions testing because the CEL light was off and that the emissions tech would not otherwise have a reason to query the car's computer. And he was right: the car passed California emissions testing immediately afterward with nary a hitch ! So glad I opted for the BG 44K experiment rather than a new cat...

Wow thats great to hear! I just poured BG 44k as instructed in my tank prior to fill up yesterday. I have until tomorrow afternoon to drive the remainder of the tank. I hope to have the same results as well....

And now the CEL light is back, 150 miles after passing emissions & 350 miles after BG 44K! That was close... I think I will look into lifting the post-cat O2 sensors as my next maneuver to get the CEL light to stay off. Really don't want fork out a grand for new cat.

At least you passed emissions. I dont quite understand what is meant by post-cat O2 sensor . When I had a indie shop check out my cats his diagnostic test said the cats were failing but the O2 sensors were reporting just fine. If you can explain what you mean by this that would be helpful for me as well.

My mechanic explained it to me like this: There is one direction of gas flow through the cat. With that in mind, there are 2 sensors: on in front of the cat (proximal,pre) and one sensor behind the (distal, post) side of the cat. The cat sensors measure the gas composition of the exhaust before and after it is scrubbed by the cat. The car's "brain" compares the 2 values in order to assess how well the cat is working. If the cat is not performing ("failing") to the relatively strict standards established by Porsche in 2006 (and which were apparently later liberalized a bit), then the post-cat sensor value will be too near the value measured by the pre-cat sensor. When the car's "brain" gets this info, it throws a CEL. Theory: if you create a gas leak at the post-cat sensor, some fresh air will leak in. This will cause the post-cat sensor to generate a relatively cleaner measurement than if there was no fresh air leaking in. Assumption: By hacking your post-cat sensor's measurements to make them seem cleaner, this will make the car "think" that the "failing" cat is doing it's job suitably because the exhaust measured at the post-sensor is now measuring and reporting cleaner exhaust with the new, fresh air leak. And this happy set of computer data will, hopefully,l convince the "brain" to turn of the CEL because it seems that the failing cat is actually doing its job. Disclaimer--I'm not a mechanic but I do like me some physics and wrenching....and not having to pay thousands of dollars just to be able to drive my car without getting some increase in performance Hope this helps!

Hi, this helps alot. Thanks for explaining it so well. Please let me know if this proposed alternative does the trick for you.