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Replacing drivers pre-cat O2 sensor......

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I finally got around to replacing this O2 sensor yesterday on my 06 TT. I was very fortunate to have my very skinny son to help me because otherwise I would have been towing her to the dealer. I removed the plastic trim covers at the rear and side of the engine bay, removed the clip holding the sensor wire to the exhaust manifold and disconnected the old sensor from the bulkhead connector.

I bought a short O2 sensor socket from Autozone and after wiring on a universal adaptor (because it would not stay on the end of a long socket bar) I was able to loosen the sensor from above the engine bay but had to extend the wrench with a couple of feet of copper pipe I have for these circumstances. The socket is a little strange to look at. It has a lug welded on one side, with a 3/8 square hole through it so when turning, the force is on the side of the socket rather than the middle but it did mean the socket is short enough to get through the miniscule gap between engine and heat shield. The odd shape, also means that the socket has to be re-positioned after only one flat. Getting the old sensor out was fairly straightforward from this point as I was able to use the attached wire to twist it out after a couple of threads. The new - and presumably old - sensor is coated with anti-seize paste which made life a lot easier. WARNING - never use the wire to assist installation as it can easily be damaged!

Putting the new sensor in is much more involved as there is no clearance to get the sensor thread started in the hole. I tried removing the wheel but there is no gap behind the liner to get to the hole. The gas suspension leg is in the way. I then removed the belly pan and found that I could just about touch the hole for the sensor and was able to poke it in from underneath while my assistant lowered it from above. My son has skinnier hands and arms than me and was then able to get under the car, reach up and around the cat far enough to start the thread which is thankfully quite short. The socket finished off the job from above. In total. the job took me about three hours and a lot of cursing. It looks to me as though a dealer would have needed to remove the exhaust system to do this job.

The good news is that my error codes have disappeared and I no longer see any misfires on the Durametric.

I hope this helps some other poor soul who might be considering a change of this O2 sensor. It looks as though the other three are relatively easily accessible. On the advice of a forum member I bought the Bosch wide band sensor online at less than one third the cost from Sunset with free delivery


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Congrats on the fix. You can get an OEM Bosch sensor from the aftermarket industry for less than $100. Exact same as the one in the Porsche box but in a Bosch box, same sensor, same plug. Food for thought next time. Front sensors are Bosch 17174 (5 wire wide band) about $100, rear are Bosch 16498 (4 wire) about $130.

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Thanks - I got the Bosch 17174 for $75 delivered.


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Maybe this will be helpful also for replacing oxygen sensor driver side before cat, bank 2 sensor 1, Cayenne turbo 2005.


Remove engine plastic covers, under car splash guards belly pan, peel back wheel well liner half way is enough. 


Trying to remove the sensor going from top was too difficult for me, the gap between the engine and heatshield is just too narrow.  I rigged up a tool from a cheap 22mm open end wrench and went in from the bottom.  I had to modify my 22mm wrench by bending it with torch and cutting a bit of the tip 24mm side (depending on the length of the 22mm wrench you may need to bent it slightly different). There is just enough room on the side of the cat for my right hand to finger in the tool, left hand reaching in from wheel well opening helping to seat the tool onto the sensor (2 rubber hoses in the way but flexible enough to push down a bit).  Once the tool was seated firmly on the sensor, I used a long screwdriver going in between the tool and steering column gaining leverage to loosen the sensor by prying at the tool (if your fingers are very strong you maybe able to loosen the sensor with 22mm wrench only).  After a few small turns it was easy enough to loosen by hand.  It is helpful to have someone untwist the sensor wire from top while it is being loosen, same with putting new sensor back.  New sensor going in is same as reverse but definitely easier if someone lower the sensor down from above.  Do not over tighten since no torque wrench can be used.  My hands size fit medium gloves.  I think there is enough room for larger hands, unless you have really large hands and banana fingers.



Edited by Loutorious

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Hi All, 


I've been meaning to post a similar procedure for 2006 Cayenne S.  I guess this is a perfect time  B)


Procedure replacing the o2 sensor for a 2006 Porsche Cayenne S.

Make sure the engine is cool.


Driver-side O2 Sensor – Bosch 17157

Passenger-side O2 Sensor – Bosch 17158


O2 sensor 22mm socket

1” and 2” 3/4 inch extension

3/4 “ratchet

10 mm socket (passenger side air box and wheel well lining)

T25 Torx screws (wheel well lining)


Driver side O2 Sensor:

1.       Disconnect electrical connector from the firewall.  The brown connector

2.       Jack up the car

3.       Remove driver front tire

4.       Remove wheel well lining (click here) for easier access to re-route the O2 sensor wiring

5.       Remove Engine Under Tray

6.       Access the driver side O2 sensor from underneath the car by the center hub. Use Pelican’s how to as reference.

7.       Once the O2 sensor is loose, pull the wirings off the various harnesses.

8.       Replace with the new O2 sensor

9.       Re-route the wiring like the old sensor.  Easier with the wheel lining off

10.   Re-connect  by the firewall


Passenger side O2 Sensor:

1.       Disconnect electrical connector from the firewall.  The pre and post cat sensors are the same color connector or black.  The inner or closest to the engine is the pre-cat sensor

2.       Jack up the car

3.       Remove passenger side front tire



1.       Turn wheel full lock to one side in order to gain better access to the O2 sensor

2.       Remove wheel well lining (click).  Access to the passenger side O2 sensor

3.       Remove the air filter box

a.       Remove 10mm bolt

b.      Pull out from the engine compartment side

4.       You should be able to see the passenger side O2 sensor from where the airbox was sitting

5.       Snake the O2 sensor socket over the wires.  Hint: remove the wire from the fastener to add slack in order to tread the socket through the wire

6.       Connect the 2 inch extension and ¾” ratchet, but in a reverse configuration


7.       Break the O2 sensor loose.  Remember, the sensor is facing in the opposite direction, so push the ratchet down or turn clockwise


8.       Re-route the wiring like the old sensor.  Easier with the wheel lining off

9.       Re-connect by the firewall








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post-105090-0-84763800-1462846347_thumb.post-105090-0-84763800-1462846347_thumb.post-105090-0-91395500-1462846708_thumb.post-105090-0-66341200-1462846706_thumb.Hi Everyone,


Well, I finally managed to purchase my first Porsche - a 2004 Turbo Cayenne with 86k miles and most of the normal out of warranty work already done (coolant tubes, cardan shaft, etc) and am thrilled to be a member of the Porsche community!  Prior to purchasing it, I read through many articles on Porsche ownership to get an idea of normal problems and remedies.  Renntech has been a treasure of information and I would now like to give back a little bit to the community.



The dreaded CEL arose after 2 months of ownership and I took the CTT into O'Reillys (thanks O'Reillys) to get a fault code read out.  It showed that my passenger side pre-cat O2 sensor was bad so I order a new one and proceeded to read through as many DIY articles as I could find on the topic.  This one and the one on Pelican Parts were most helpful and are what I used as my basis.


My initial plan was to remove the inner wheel well per sswong98"s good details above.  I started down this path, took off the wheel and decided to take a peek underneath before removing the wheel well simply to assess how much room I had to work with.  To make a long story short, I ended up being able to remove and replace the O2 sensor within the very confined space given and without removing the wheel well.  In all, it took 90 minutes after jostling about quite a bit and trying different tools.  I thought this might be another alternative of value to offer to this community so I'll describe it briefly here.


1) Follow SSwong98's steps of:


a) jack up vehicle

B) turn wheels right ​to wheel lock

c) remove front passenger tire

d) remove 02 sensor electrical connection at firewall.


At this point you can see how much room I had to work with between the body, suspension, etc.  The photo with the end of the 3/8 ratchet extension shows where to view and then subsequent photos show the amount of clearance and the 02 sensor.


Basically, I was able to use a 22mm open ended wrench and get it into the space shown in the photos.  Lying on my back, I was able to get the wrench between the suspension and inner wheel well and break the 0@ sensor loose.  Once I had it broken loose, I could use my fingers to unscrew the O2 sensor, again lying on my back and from underneath the vehicle.  Unscrewing the )2 sensor was not difficult but took about 5 minutes as I could only turn it slightly, then re-grip the sensor so that the wire did not cause it to screw back in, and then continue this process until it was removed.  I could have also cut the sensor wire which would have eliminated some of the torque produced by the wire and made it slightly easier to unscrew the sensor.


Once the sensor was out, I removed the original heat shield from the original O2 sensor wire by cutting it lengthwise.  My goal was to reuse it on the new sensor.  I then drilled 4 small pilot holes on both side of this heat shield (sorry, forgot to take photos) and placed a pop rivet into each in order to have it hold in place around the O2 sensor wire.


The most challenging part was getting the new 02 sensor started into the mounting hole.  I dropped the sensor in from the top of the engine and was able to locate the sensor quite easily.  I was also able to reach up from underneath the vehicle, grasp the sensor with a thumb and finger and get the O2 sensor into the mounting hole.  However, once again, the sensor wire created a torque that prevented me from being able to start the sensor correctly into the threading.  After trying various options for 5 minutes, I called in the calvary...  I asked my son to hold the sensor wire from the engine bay side and to turn the wire slightly in a clockwise manner so that the sensor wire torque worked in my favor.  I also repositioned myself so that I could get a much better grasp of the sensor.  Instead on lying on my back looking up at the sensor, I sat down in front of the caliper and was able to reach the sensor through the same opening as before.  While I could not see the sensor, I had it placed into the mounting hole from before so all I needed to do was to get it to start threading properly.  In this seated in front of the caliper position, I was able to much more easily grasp and turn the sensor and got it threaded within a few seconds.  At the same time, I told my son to slowly keep tuning the sensor wire.  Once the sensor was hand tight, I used the 22mm open ended wrench to tighten it.    All told, it took about 90 minutes from wheels up to wheels down.


Some other notes:  I ordered the special O2 sensor socket from Pelican (same one shown in SSWONG98's write up) but, very oddly, could not get enough room from the top or bottom to be able to get it onto the sensor.  Removing the inner fender well would have helped here.  I also would suggest getting a stubby 22mm open ended wrench as this would allowed more freedom for movement.  The one I had was about 14 inches long.  I also had a line wrench (shown in one photo) that was a bit shorter in length and worked very well.


Well, I hope that this is some value to this great community








Edited by jweimer

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Glad my post helped.  My Cayenne S doesn't have turbos (I wish), there is a little more space  :eek:

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How were you guys able to get it from below? The steering shaft is in the way, from behind and beside the driver side flex pipe entry! From top, there is only less than 15mm space to reach or see anything. I'm stumped. 2006 Cayenne Turbo.

Edited by Zuffenhausen955
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