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

[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