Oxygen (O2) Sensors

15182 Oxygen Sensor - OE Type Before Catalyst

15183 Oxygen Sensor - OE Type After Catalyst

15738 Oxygen Sensor - Universal Type Before Catalyst

15738 Oxygen Sensor - Universal Type After Catalyst

2004 986 Boxster 2.7L or 3.2 L

16506 Oxygen Sensor - OE Type Before Catalyst

15506 Oxygen Sensor - OE Type After Catalyst

15733 Oxygen Sensor - Universal Type Before Catalyst

15733 Oxygen Sensor - Universal Type After Catalyst

The difference is that the Universal parts do not contain the already fitted wiring harness and you must use the one from your existing and crimp attach (DO NOT SOLDER) it to the new sensor. The difference between the OE before and the OE after is the length of the harness. Better to get the OE type. No need to pay Porsche prices. Buy the Bosch ones online.  http://www.oxygensonsors.com has a generic part for $114 with harness for 2 sensor 2 cat cars. Since I wanted the OEM version without the Porsche markup and I needed the shorter harness version for the 4 sensor 4 cat car, I bought from AuohausAZ for $143.16 delivered, when the list on the part was $261.

Even Cheaper But More Work 

On the 986boxster forum, there is talk of using a USOS-4000 part from Speedy Auto Parts and reusing the existing  pigtail by crimping it (DO NOT SOLDER) it to the sensor and then using heat-shrink tubing to cover the splice. This part goes for less than $40 each! Or from Parts Train who has better shipping prices. Or at Auto-Parts-Warehouse for $26.

Change 2 or 4?

When you get a “Tired Sensor” code on the OBD2 reader, it is telling you that the sensor is not reacting as fast as it should. Therefore the engine computer isn’t benefiting from the feedback from the sensor and is probably making bad decisions based on outdated information. The result is a waste of gas (poor mileage) and/or a dumping of the wrong mixture into the catalytic converters which can cause them to go bad (big $$$).

Some mechanics will try and tell you to replace the 2 matching or even all 4. You don’t need to do that. They are supposed to last 100K miles. The computer will tell you via codes when they are starting to fail. But that means you have to occasionally read the codes as the "Tired Sensor" codes doesn't cause a check engine light. Perhaps the thing to do is be sensitive to the way the engine runs at startup and, at any abnormality (stumbling. rough running) check the codes with a code reader. That way you can get the sensor replaced before it goes totally bad and causes $$$ damage to the cats.

Covered by Warranty?

Read your warranty as it varies by state. For example, in California the answer might be yes while in Virginia the answer to the same set of facts as to in-service date and mileage might be no.

Change them yourself?

If you are young and supple or have access to a lift, absolutely. This is a trivial mechanical job. 

If not, see your Porsche mechanic. He should charge no more than 2 hours (book rate times whatever his hourly rate is plus whatever fees he tacks on for waste disposal, etc) to diagnose, replace the O2 sensor (most of that waiting for the cat to cool), reset and test drive. 

Or take the part you saved on by buying the Bosch part by mail order  to your local muffler shop and negotiate a half hour labor charge. They have the lift, and the tools, there is no special knowledge needed. I know there book says more but you've done the diagnosis and have the part in hand so it is a simple put the car on the lift, remove, replace, lower the car process.

The actual replacement takes perhaps 5 minutes. There should be some time spent rechecking after a short drive to make sure the code is now still clear and the new sensor isn't defective. But the codes that indicate sensor failure are so explicit that replacement usually solves the problem. I've gotten the replacement only done for as little as a half hour labor charge when I didn't have access to a lift to do it myself.

Here is where they are located on some aftermarket headers/catalysts and on some stock ones.

They are the holes in the top (aftermarket) set, the sensors are the things with cords attached on the bottom (stock) set. This picture is from a later Boxster, one with 2 sets of sensors.

The connection looks like this. To find it, trace the blue wire back from the sensor. To disconnect the plug from the socket, you press down and in on the center section and then pull.

 These pictures courtesy of shumtoby.

The sensors are installed with a torque of 55Nm/41ftlbs using a short handled torque wrench. I installed mine tightly without worrying about the torque. Purists would object.

Which Side is Bank 1? 2?

The code will tell you which side and before or after. "Before" means the sensor closer to the engine; "after" means the sensor nearest the muffler.

This picture shows the engine as you would see it with the access cover behind the seats removed. Left on this picture is the passenger side on a US car. Cylinders 1,2,3 (Bank 1) are on the passenger side of a US Spec car.

The error codes  involved with the O2 sensors (for a 1997-1999 DME 5.2 car) look like this. There are separate lists of codes for '97-'99, '00-'02 and '03-'04 cars due to the differing Drive Management Electronics (DME). Rather than list them all here, I will provide this link to www.renntech.com's Boxster forum. Once there, select 'Quick Menu", then select "OBD P-Codes", accept the disclaimer that you won't post the whole list, then select the DME codes for your year Boxster (986) '97-'99 DME 5.2, '00-'02 DME 7.2 or '03-'04 DME 7.8. Basically, they look like this.

Tools Needed?

You can remove the O2 sensor with an adjustable wrench. There are also special sockets and wrenches sold that have a cut-out that allows the wires to fit through a slot while the socket turns and which allow the use of a torque wrench. You need a 22 mm metric. The special tools cost from $15 to $30. 

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