Finally replaced all 4 O2 sensors w/ generics for $160.

[MNBoxster]

Originally Posted by fab

Ohioboxster, are you sure?
I thought P1117 code refers to the Precatalyst oxgen sensor. This infomation is from Bentley Service Manual.

MNBoxster you must like to type alot, unless you like using copy/paste.
thanks for the lenghty email but what you wrote how does that answer my question.

?-
How can you tell out of the which sensor needs to be replaced?

Hi,

You have a 2.7 e-gas Boxster while OHBoxster has the 2.5 non-e-gas model. Different code definitions for each.

But, a Bad O² sensor can throw one of many codes, usually all related to AF Mix, ECU, or actual O² sensor.

If you read my reply, and if your Boxster has 30k+ mi. on it, you'd see that you need to replace all the sensors, not just the one which is showing itself to be faulty at present. These have a Service Interval which is mileage dependent (30k mi. according to Robert Bosch, AG), just like your Oil & Filter, and they all have been in service the same amount of time/#miles .

You should replace them all at once. Not doing so may lead to no improvement in performance/range/emissions (you might not even feel a difference, but the DME may not be selecting the optimal Maps for your car/gas/driving conditions). And, you'll most likely be starting down a path where the other three require attention in short order...

Happy Motoring!... Jim'99

[ohioboxster]

Jim,
I used his cars information when I punched it into mt DTC look up software.

[MNBoxster]

Originally Posted by ohioboxster

Jim,
I used his cars information when I punched it into mt DTC look up software.

Hi,

OK, my misunderstanding. But, your code description is still in keeping with bad O² sensors. If the signal from the sensor is non-existent, then a code speaking directly to the sensor will be thrown.

But, if the sensor is sending signals which are outside what the DME has been programmed to expect, it gets confused. It doesn't fault the O² sensor because it is getting a signal from it. But, it can't find any Maps to use which correspond to the signal values from the sensor, so it will code that the DME (Mfr. AF Metering) cannot function properly because that's all it knows, it doesn't know the O² is bad since it is getting an actual signal from it. An O² sensor can fail outright or it can fail progressively, sending signal values (voltages) which the DME has not been programmed to identify or interpret.

In this specific case, it could actually be one bad O² sensor, or any/all of them, which is one reason you want to change them all at the same time. They're not like lightbulbs, where you simply replace the burnt out one. Instead, they are all linked as a part of a system. Unfortunately for the wallet, this system is only as good as it's weakest link. But that doesn't mean the the remaining sensors are operating properly. Zirconia sensors work by exposing a certain surface area to Oxygen in the exhaust stream. Over 30k mi., this surface area is reduced as carbon and other contaminates condense from the exhaust stream and onto the Zirconia surface, meaning that Oxygen is now denied to that surface area, and the voltage(s) which the sensors produce decline with time as well. It is the value of these voltages which the DME uses in determining the optimal AF metering for the conditions the sensors are telling it are present.

These kind of codes are the ones which require that you put on your detective's hat to figure out what it is exactly which is causing the AF Metering to function improperly. A bad MAF can also throw similar codes as well in addition to throwing a bad MAF code. Hope this helps...

Happy Motoring!... Jim'99

[xclusivecar]

Everyone should listen to Jim on this one...I've been there done that! Once one goes they will all start setting codes and if you replace them one at a time you'll spend more time in the dealership than any of us would like to. Luckily my extended warranty covered them...but only as they expired...so I ended up dropping my car off at the dealership once a week for a month! PITA!!

[ohioboxster]

Well, for the record I dont believe anyone disagreed with Jim. We know hes a knowlegable guy.

[socratic]

I've been reading this thread with interest.
I'm at 47,500 mi on my non-S 2001, purchased about 1.5 years ago when it was at about 30 to 35,000. I can say that my car runs as fine as I remembered it at the time, but then again, there might have been a gradual deterioation since then.

My question is how do I know they need replacing? There are no cel lights yet and the car is feeling fine. As per MNBoxster, I should be way over the 30,000 mi sensor life limit.

Also, how good are the discounted ones? The Speedy/PartsTrain guys are selling them at approx $35 each. The OxygenSensors.com guys are at $114 and even then are considerably cheaper than Porsche. Is this case an exception to the rule of you-get-what-you-pay-for?

[KevinH1990]

Having just experienced a Mass Air Flow sensor failure at a bad time, I'm contemplating the replacement of my O2 sensors before they have a chance to fail. (I generally like to choose the place and time of my disasters.)

I'd just go ahead an do it if it weren't for the expense of the OEM sensors. I'll keep an eye on this thread for the next few months. I hope Jim keeps us updated on how well this is working.