flmont

My new to me 02' 2.7 with 80 K miles had the CEL come on its a solid light not a blinking lite the shop I took it to said all the O2 sensors were bad, now how could that be,.I asked for a ECU check or a durometric check I don't think they did it there was no print out offered to prove anything I was being told,..so Iam not sure if Iam getting the correct info from them..?? Thanks Frank

Starter986

Unlikely all went out at once. Go to another shop. Get a code reader... $40-$80... My money is on one sensor, maybe, and a code will reveal upon which side of the car and, likely, which specific sensor. Could be a leaky gas cap... gotta have the code(s).

Everything I know about my car I've learned from reading a lot of posts upon this forum... and another. That said, I'd not be returning to the garage that said all went out, and without documentation to support that diagnosis.

Keep us posted.

Anker

No, but cats can be destroyed on both sides at once. What were the codes?

Macster

What others have said regarding sensors failing all at once. Very very unlikely. I've been through several sets with my Boxster and one set with my Turbo and in every case what prompted the change was just one sensor flagging an error.

Now I will say that if one is bad and at 80K miles my advice would be to replace them all. Otherwise you can end up with a real responsive sensor with 3 slower to respond sensors and engine fueling while not bad enough to trigger a CEL could very well be sub-par.

Due to a CEL and a sensor error code (bad heater circuit) I had all 4 changed in my Turbo at 132K miles. Except for the CEL and error code the engine manifested no untoward behavior.

To my mild surprise, after all 4 were replaced the engine ran better. That the engine ran better after new sensors underlined the point that even if sensors are not triggering error codes their performance can still deteriorate and at some point replacement is a good idea even though there are no active O2 sensor error codes.

Likewise I had all 4 sensors replaced in my Boxster at around 305K miles only though one was flagging an error -- which I don't recall now what it was -- and the engine ran better afterwards. I don't recall how many miles the sensors had either but it could have been close to 200K miles.

mikefocke

O2 sensor codes are very specific as to cause. Before swapping expensively, ask for the specific codes and make sure the guy reading them has a Porsche specific code reader. Post them here and we'll look them up for you.

More info on the sensors and their function is here.

flmont

Great mike ,..Thanks I will but it will take a week or so !!

Porschetech3

02 sensors don't all fail at once, just like all spark plugs and coils don't all stop firing at once.

02 sensors used to not last any longer than 30k-50k miles. Then the EPA started pushing oil/fuel companies and manufacturers for longer lasting emission parts. The main reason Zinc and Phosphate was removed from engine oils is to help Cats and 02 sensors last a minimum of 120k miles.

Like Doug said, if you have one that failed, the others that have been ran under the same circumstance, are not far from setting a code also. New 02 sensors have a switch rate of 5 times per second, after they slow down to about once every two seconds they will set a code.

Just change them all with fresh ones, if you got the bones.

Brian in Tucson

I just ordered a set (all 4) of Nippon Denso O2 sensors from rock auto. With shipping and the 5% discount, they came to $280. My inclination is to do them (on a used Porsche) at the same time as a comprehensive tune up--plugs, coils, tubes, AOS. And every other tuneup thereafter.

Hard to tell if the OP has bad sensors, other than the kick in the wallet, it wouldn't hurt to change them out. As Macster pointed out, new good quality O2 sensors can help with performance, efficiency, and emissions

Whats not to like? (Note, I do all my own work, so labor is not a consideration.).

(Why Nippon Denso? I've been working on cars for about 40 years and never got a bad Denso part. Great confidence in their parts.)

Brian in Tucson

As usual, a great writeup from Mike's site!

flmont

Once they are replaced how do you clear the code is it automatic ( they are not replaced yet ) Just checking ,..Thanks.

Brian in Tucson

aAfter a certain number of cycles the codes will clear. Or you can disconnect the battery for a few minutes and it will clear the code.

mikefocke

But the disconnect of the battery, while clearing the code, will also destroy any data the ECU was using about the particulars of your engine. So it takes a few days and drive cycles to get from a base set of values to ones the ECU has learned are correct for your engine. So it won't pass the smog/MOT/emmisions test for a few days even if the O2s were the cause.

I'd bet there was some other underlying cause. Sure hope the CATs haven't been used up.

flmont

Me Too,..it passed emissions the day before I bought it,..a Saturday,..then Sunday run around to get the feel of it ,..and coming home the light came on so yea,..I hope just O2's Cats would suck,..but the shop said O2's just all 4 of them..LOL..at once as we know !