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

[fab]

ohioboxster,

How can you tell out of the 2 which sensor needs to be replaced?

My CEL came on last week with a P1117. It hasn't come back on TG.
I'm hoping it doesn't but if it does I am going to pay 147.00 for a Bosch sensor. From thiis website
http://www.automedicsupply.com/index.php?&model=Boxster&stopredirect=yes&width=1024&height=768

[MNBoxster]

Hi,

Using Universal O² Sensors isn't an issue if you do your homework. There are 5 types of O² Sensors; Unheated Thimble-type O² Sensors (LS), Heated Thimble-type O² Sensors (LSH) , Heated Titania-type O² Sensors, Heated Planar-type O² Sensors (LSF), and Heated Wide-Band O² Sensors (LSU).

Further within these types, several different primary materials are used and two different methods of extrapolating the Air/Fuel Mix are used.

A sensor using Titania, changes it’s resistance of a reference voltage (sent to it by the ECU) which will change proportionally to the amount of Oxygen it is exposed to. This technology was never in widespread use and was found only on a few cars from the mid-80’s to mid-90’s. It is estimated that fewer than 3% of all cars and trucks use this type.

The most prevalent types of O² sensors on the Market are those which use a ceramic made of Zirconia. When exposed to Oxygen (O²), a Zirconia ceramic will produce a voltage proportional to the amount of Oxygen it is immersed in (Exhaust stream) as the Oxygen molecules embed into the ceramic’s surface. For the two types of Zirconia sensors, they need to be heated to 650°F. This further breaks them into two additional categories: Unheated and Heated.

Unheated Zirconia sensors generally have only one or two wires. Their advantage is that they are simpler to manufacture and are of the earliest technology. Their disadvantages are that they contaminate sooner (as carbon and other combustion by-products condense on the exposed ceramic) and on Cold Starts, don't allow the ECU to function until the exhaust gasses bring them up to their operating temperature (Open Loop). Also, if idling for extended periods, they can fall below their operating temperature threshold (650°F) and force the Car's ECU back into an Open Loop where the ECU is no longer monitoring or responding to changes in the A/F mix. This affects both emissions and performance.

Heated Sensors contain a Heat Coil which is fed by a separate voltage circuit and usually have 3 or 4 wires. Their advantages are that they come up to temperature sooner and don't stop monitoring at idle. Also, since they are heated, fewer contaminates can condense on the ceramic surface of the sensor giving them a longer service life.

Heated Planar-type O² Sensors (LSF) and Heated Wide-Band O² Sensors (LSU) are a much more modern technology and are used primarily on only the latest model cars. They use a circuit board with the sensors attached and use a pulse-width heater coil. Their advantages are that they operate at much higher temps (1292° to 1472° F) and will vary their voltages in much smaller increments allowing for direct sampling of the A/F mix instead of an extrapolation method used on the other types of sensors. I won’t discuss these in-depth except to say that the ’08 997TT uses the Heated Wide-Band O² Sensors (LSU) type. Hope this helps.

Zirconia O² sensors are the type used on the Boxster (Heated Thimble-type O² Sensors (LSH)). Because all air does not contain the same amount of Oxygen (changes in altitude, Ground Level in Stop & Go Traffic, etc.), Zirconia sensors also need to sample reference air. To do this, they either have a hole at the base of the detector, or sample air drawn-in from the electrical connector and sent to the sensor inside the wire sheathing.

This is where most people trying to use Universal Sensors will get into trouble. They will inadvertently block the reference air from the sensor by using the wrong connectors (which contain no sampling hole), kinking the sheathing, or by using heat shrink tubing and also blocking the sampling hole. When using Universal sensors, you need to carefully examine the new and old sensors. If the sampling hole is in the sensor body, there will be no problem. But, if the reference air sample is drawn into the connector, you need to make sure that you don’t interfere with this function when attaching a connector. The Bungs for O² sensors are standard, so virtually any Universal will work so long as you account for the air sampling to occur.

O² sensors have a usable life of only about 30k mi. (source: Robert Bosch, AG). After this, range (MPG), emissions, and performance can suffer. Changing them at this interval is one way to breathe new life back into your car and the cost is significantly offset by fuel savings. You should change all the O² sensors at the same time as they are mileage dependent. You can confuse the ECU (DME in Porsche parlance) by mixing new/old sensors causing a loss of range or performance. And, if you have 1 bad one, you'll soon see the others fail as well, especially if over 30k mi. of service, so it's just generally easier to do them all at once (save on S/H, installation, etc.). Hope this helps…

Happy Motoring!... Jim’99

[ohioboxster]

Originally Posted by fab

ohioboxster,

How can you tell out of the 2 which sensor needs to be replaced?

My CEL came on last week with a P1117. It hasn't come back on TG.
I'm hoping it doesn't but if it does I am going to pay 147.00 for a Bosch sensor. From thiis website
http://www.automedicsupply.com/index.php?&model=Boxster&stopredirect=yes&width=1024&height=768

P1117 is the code for the maf sensor, I used an Atron hand held scanner that I bought off of e-bay for $55.00 it comes with a code cd,will turn off the cel but wont give actual information about sensor like voltages and such

[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?

[ohioboxster]

Sorry, I just punched the code in my program and it said " Manfacturer control fuel air metering" If you hook a scanner up to the OBD II port under the drivers side dash it will tell you which 02 sensor is bad. One of the guys on the forum informed me Auto Zone will scan the car for free. You could buy one of these , thats what I did.

http://cgi.ebay.com/Actron-Code-Reader-CP-9135-OBD-2_W0QQitemZ260036047969QQihZ016QQcategoryZ92078QQr dZ1QQcmdZViewItem

I bought one for 55 bucks so it worth it to look around on e-bay.

[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!!