CEL---- o2 sensors

Guys, my car is at the stealership for a 30k service. On the way over there, the CEL came on, no problem I thought, I am going to the service center... Anyway, the reading shows a bad o2 sensor, but they cannot repair/replace or confirm the error because I have a custom exhaust... headers, high flow cats, mufflers. They recommend replacing all parts to OEM and run it stock to get rid of the code. I recommended they check in to the local psych ward. Since they cannot guarantee any results, my dilema is, should I just pay them to replace the o2s and risk the light coming back on? Should I shell out the money to replace the cats that they think are bad and replace o2s? I don't want to restrict my system, as it is full exhaust, intake, and programmed. I also don't want to spend 3k dollars for a meaningless CEL. Otherwise, I can clear it myself and ignore it for as long as possible, but what is the downfall of running with bad o2 sensors. I need to pick it up tomorrow or I need to tell them to repair it, i will be trying the other boards as well.

It is much cheaper to replace the sensor. Buy it yourself at suncoast and install it yourself. To clear the code you will have to disconnect the battery. Just remember that you will need your radio code. If the dealership is planning on replacing the MAF sensor anyways, it might be worth giving it a try.

Thank you for the quick response. Well, the crooks charged me 130 dollars to diagnose the engine code... which they failed to mention when I dropped it off. This can be applied towards the repair if I have them do any sort of repair, so I was thinking to just change them anyway since I had 140 dollars worth free.

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You have a code indicating a bad O2 sensor or you have an code which is the O2 sensor giving an error? I.e. the O2 sensor will set off a CEL if you are running rich or lean for any number of reasons which is an O2 sensor related CEL but not an indication of a bad O2 sensor. What's the code?

No, running rich or lean I would be OK with. He said it is indicating "failing sensor" which leads me to believe I should replace them. BUT, he said doing so is worthless without reverting the exhaust to stock form, which is not an option.

First please tell us what the car is. Second, get the actual code (since you were ripped off $140 for it it is yours). Post the numbers here so we have a better idea. The guy sounds like an idiot as plenty of O2 sensors work with aftermarket exhaust. It could be as simple as it came unplugged or was plugged in wrong....post the codes please.

... or it could also just be the MAF, as they will throw out flags on O2 sensors.

Yeah I will see what I can get from them in the morning. The car is a 99 c2 Will post more info as it becomes available.

Nice car! How many miles? One question. How long ago did you upgrade the exhaust? 1st thought that comes to my mind is if it's run with that exhaust system for a good while, then it has nothing to do with the o2 sensor failure. 02 sensor's do go bad after a while (100,000+ miles). Sounds like this guys making you diagnose the car so he won't be responsible if his repair doesn't work. I'd say take the car somewhere else and call it a $140 lesson (pretty cheap lesson in the Porsche world). Did I say that's a NICE car??

From time to time I do have a CEL too (code 1276); it started with the aftermarket headers that I put on my '00 C2 (42k miles); aftermarket exhaust alone didn't trigger CEL. Last time it popped up, I just checked the code with my OBD II reader and erased it. However, the time before I had this code I cleaned my MAF (I had the same code together with a MAF related code when my MAF went bad after the K&N CAI install). However, it can be that there's an air leak somewhere in the exhaust system that triggers this CEL which I'll check when I've my car on a lift next time. If there's no leak and the CEL comes back, I plan to change the O2 sensor. Car runs great and it doesn't harm the engine even if the O2 sensor would be bad.

Unless I'm crazy the exhaust itself would have to be awful for it to throw enough grime back to the O2 sensors to cause problems. headers miiight be able to cause problems, but before you go paying people money for labor, ask your dealer if you can apply the 140 bucks you owe them to new sensors from the parts department. Then crawl under, inspect, replace yourself and reset. That's what I'd do

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That f@cking blows. Next time the CEL comes on, go to Autozone and ask to borrow their code reader for 5 minutes. It's free. You could try clearing the code and waiting to see if it comes back.

Thanks for all the great responses guys. The car has 40k miles on it. Since the fluids looked especially dirty and I do not know the full history of the car, I had them do the 30 service. The exhaust system is suspected to have been on since 99. I didn't install it. The car was owned by a porsche service manager for the first 20k miles, so I would imagine things SHOULD have been done correctly. If they allow me to do it, I will be applying the diagnostic fee to the parts and leaving with them as suggested. I will not be back to the dealership after this service. They gave me just enough bad taste to lose my business. Which blows my mind because with the economy the way it is and the ability to use internet for car shopping, it seems like dealerships would be treating customers like kings to keep them happy.

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Ahh, the joys of getting to know your local Porsche dealer and learning to bend over when instructed and take it without lube.

my cel went on the other day without anything unusual in the engine bay. i figured o2 sensor or maf since i had the evo intake installed last year. also, i tightened the gas cap. i cleared it by disconnecting the battery, will watch it closely before i go to the dealer, i'd go to autozone first if it comes back on.

On my old 99 C2 the CEL light came on and the dealer told me it was the O2sensor, which I had replaced. Two weeks later, the CEL light came back on and the dealer said it was the MAF, which was fixed. Two weeks after that the CEL light came on and I was now pretty pissed. The dealer said it could be "any of a thousand things"...and was charging me around $800. a pop! I traded the car in for my current ride...with a CPO. Be careful!

This happened to me and my car is heavy modded. Ordered the 4 sensors and screwed them in myself...... very easy to do on my car but then again, my exhaust is easily accessible and has no mufflers.

02 sensor shouldn't go bad at 40,000 miles. I'd do some more checking before I replaced the 02 sesnors. Like mentioned, go to Autozone and get the code read, then clear it. If it comes on again, get it read again to make sure it's the same fault code. My experience with 02 sensors (minimal) says they sould last at least 100k miles.

Get a code reader they are CHEAP and avoid the hassel. My O2 sensor throws a CEL every few months and I reset it and I'm off. Dealer is 100 miles away, code reader in trunk and ready to go.

I'm betting that the codes show a left and right bank O2 flow error. (I'll look up the codes later) and that will be indicative of a MAF problem.

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for some reason I thought the OP had ruled out MAF. If you haven't, at least inspect it, try cleaning it, and by all means buy a durametric or a code reader and reset the codes, wait for them to reappear

I agree with all the above. An Actron code reader reset tool will cost less than your trip to the stealer. The cat code is just emissions and does not affect performance and you may still have a code after replacing sensors. If your MAF is bad you wil know it, the car will run like crap. I reset my CEL every 100 to 600 mi because of full exhaust and my SC. Will

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Well, if he doens't have the codes I'm not sure how he could rule out the MAF As for the MAF making the car run like crap, that's not necessarily true. Mine ran fine when it was throwing up codes and needed replacing.

Does the dealer say that all four O2 sensors failed simultaneously? It would make me wonder unless, of course, someone peed in the gas tank...

I got my car back today and read the dang thing myself- p1123 is my code.

only one code?

If you were getting P1123 and P1125, then I'd say MAF, but with only one, then I'd revise my opinion. P1123 Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Lean Threshold Probably just that one sensor on it's way out, but here's a link to a discussion over at Renntech that might help diagnose other possibilities. http://www.renntech.org/forums/index.php?showtopic=3834

A code 1123 DOES NOT indicate a bad O2 sensor. It indictaes that bank 1 on the engine is running rich. Very often, this code will be accompanied by a code 1125 which means bank 2 is running rich. This code is only generated at idle or closed throttle. Your O2 sensor is working fine. This code may be a fluke and resting it may solve your problems. It could also be caused by a leaky injector on bank 1. Run a can of injector cleaner through the tank. If the 1125 code finally appears, clean your MAF.

Yeah, just the one code right now. I do not believe they ever re-set it. I did so and will run it tomorrow and post results. I appreciate the great help guys

You're running rich, your O2 sensor is probably fine because it's telling you you're running rich, the engine is trying to adapt by adding air and hitting it's lean threshold. Any other symptoms? Where are you located?

South Louisiana - exhaust system consists of evo intake, phoenix headers/ high flow cats/ mufflers unmarked... It is as loud as a truck with a missing muffler