Oxygen Sensor

[RNajarian]

Every 3-4 weeks for the past 4 months I've been pulling A CEL Code relating to either the O2 sensor or the Cat.

My car is a 2000 Base Model 986 with 140,000 miles. O2 sensors are the original ones put in 10 years ago in Germany. Logic tells me it is probably a bad O2 Sensor.

I did hook the car up to my Durametric Scanner and read the voltages. The numbers were within spec at that time. I have noticed I pull the codes when it is cold outside (Southern California, 50 degrees is cold for us)

I'm looking to change bank 2 first (both pre and post cat) then bank 1

ANY thoughts on which Sensor to buy? I'm leaning towards the Bosch OEM sensor sold by our host, however if any one has had any success with any other brand of O2 Sensor I would be glad to hear your opinion.



Thanks

[Wayne 962]

I had a problem using the non-OEM sensors, I would go with the BOSCH ones. The heater element might be dead inside the O2 sensor, hence the readings only on cold days?

-Wayne

[mikefocke]

I don't follow your logic
in changing one side and then the other. Usually the codes in this area are pretty specific as to the sensor they relate to. If in doubt, post the raw code here and someone with the ECU/DME manual will interpret them for you. The pre-cat (closest to the engine) sensors are usually the first to go. I would agree with Wayne, I've used the Bosch sensors with pigtails attached from the factory with much success. To me there was no risk of a wrong part and no risk I'd crimp the wires badly or not get the electrics watertight but I also didn't have to pay the car manufacturer's prices. Bosch is what Porsche buys, after all....and if they lasted 100k, you got about double what most people get out of them. They are worth replacing because, if the cats get fouled, you are in serious $$$ trouble and installation hassle.

Part numbers and a how-to here.

[RNajarian]

Good Suggestion Mike.

Here are the codes I've pulled since December 23, 2009.

Dec 23, 2009
P1118 Porsche Fault Code 4 - Heating power O2S behind Cat c. bank 2
P0430 Porsche Fault Code 45- Cat conversion bank 2

Feb 6, 2010
P1118 Porsche Fault Code 4 - Heating power O2S behind Cat c. bank 2
P1117 Porsche Fault Code 14- Heating power O2S behind Cat c. bank 1

Feb 20, 2010
P0430 Porsche Fault Code 45- Cat conversion bank 2
P1265 Porsche Fault Code 301- Crash Signal

The P1265 Code is unusual since it does not relate to the emissions system. Apparently it is an airbag code, signal implausible. I reset the codes, hopefully that one will not return.


Based on these three cases I believe the post cat sensor (bank 2) is bad since it tripped the CEL on 12/23/09 and 2/6/10. In addition, the post cat sensor (bank 1) is probably bad since it tripped CEL on 2/6/10.

The P0430 code indicates the catalytic conversion is too low. I am have read a few bottles of Techron will improve combustion and improve emissions. I am not sure how helpful this will be since I usually use Chevron gas anyway.

What do you guys think?

Both POST CAT Sensors definitely. Should I do the PRE CAT sensors?

And finally, I hope this isn't a silly question, what does Starter Cat Mean? Is the Post Starter Cat O2 sensor the closest to the rear bumper/muffler?

Thanks

[Wayne 962]

Here's a blurb from my new book on using non-OEM 02 Sensors:

There are two different types of sensors you can purchase – generic ones that allow you to snip the connector off of the old sensor and put it on the new one, and original OEM sensors with the correct connector. On older cars, I used to use the generic sensors, but I’ve had problems with using them on these newer cars. Researching further, I discovered that the wires and connectors are very important on these O2 sensors. The Porsche factory workshop manuals state the following:

“911 Carrera 4 has a new, water-proof oxygen sensor. Water-proof means that the upper sensor section and housing are connected leak-proof with a later welded seam and previous reference air openings are omitted. Reference air is now taken via the connecting lead and plug connection. For this reason it is important to keep contact solutions, lubricants, liquids or similar products out of the 3-pin plug, since they would lead to sensor failure”

Soldering wires together can interrupt the reference air signal and lead to problems with the sensor. I’ve also had problems with the Bosch factory Posi-Lock connectors that are supposed to work with these newer sensors. Because the relationship between the connector and the O2 sensor is so vital to the proper reference signal, I recommend that you only use the correct sensors with the proper plug.

It sounds like your heater elements are going in the O2 sensors. I believe these are mostly used to get uniform values upon startup, so no huge ding on performance there. Probably emitting higher emissions when you start up though. Could be a wire harness issue as well, but typically not.

-Wayne

[RNajarian]

Thanks to everyone for your input. The write up on the O2 sensors from your book was great Wayne. Can't wait to pick one up.

Looks like I'm going to be ordering two post cat sensors tonight. And I think they qualify for free shipping.

[Wayne 962]

Originally Posted by RNajarian

Looks like I'm going to be ordering two post cat sensors tonight. And I think they qualify for free shipping.

Yes, they do!

-Wayne

[mikefocke]

I'd suggest there are more options than the ones Wayne has listed if you divide them this way:

1. Walker generic sensors without any wiring (often seen on eBay).

2. Bosch sensors without any wiring

3. Bosch sensors with Porsche model specific wiring and connectors

4. Porsche branded sensors with Porsche model specific wiring and connectors

With the Walker brand, there are people who have made them work and people who absolutely say they don't work as they give out a different profile signal than the ones Porsche tunes its ECU to.

With the Bosch brand without wiring, you become responsible for the crimping (the factory does it on an expensive automated tool and then tests the results) and weather-tight sealing. Plus you are reusing wires that may themselves be part of the problem.

The Bosch sensors with wiring and connectors are exactly the same ones Porsche uses, spray paints on a Porsche part number and repackages in Porsche branded packaging. They often cost less than half what the Porsche branded ones cost. I've used 2 of these in the pre-cats of my '01S and both worked just fine. They come in 2 different part numbers because they have different lengths of wiring (same sensor) for use in the pre or post cat sensor positions. Get the right one.

[Wayne 962]

Right, I agree with Mike, I like choice #3 - the BOSCH OEM ones. Sorry if that wasn't clear from my previous posts...

-Wayne

[RNajarian]

Thanks Guys. I'm looking at the Bosch sensors with the connectors right now. Fed Ex just delivered them. I plan on installing them this weekend.

Thanks again for your insight.