Has anybody done this job? Mine's failed at 43k miles and I bought a new one and crawled under the car to replace it today. You need to pull the back skid plate, which isn't that difficult aside from some bolts which aren't immediately apparent until you realize that it's not coming down after replacing all the ones you can see.

Anyway, the problem is that once you get the skid plate out of the way, you can see the sensor up there, and I can get my wrench on it, but there's no room to turn the wrench. The front driveshaft is right where you need your hand to be to turn it. I think there are two options:

1. Buy a 22mm crows foot wrench and try to use a long extension to get it loose.
2. Drop the front driveshaft

It has to be one or the other. There isn't enough space as is to work up there. In fact, I couldn't even really get my hand on the connector to unhook it, so #2 is sounding even more like the way I need to go.

The manual that I downloaded is worthless. There isn't any procedure for anything except dropping the entire exhaust.

Front propshaft off

There is a special tool to remove the shaft from the diff coupling

OK, job is done. No need to remove the driveshaft/propshaft. In fact, I don't recommend it since removing the propshaft is difficult. Doing it the way I did it isn't easy either, but it will save a couple hours over removing that shaft.

Here's the tools that I used:

1. Bent handle Oxygen Sensor wrench, with a jack handle to act as an extension
2. Long flat blade screwdriver
3. 16mm and 10mm sockets, ratchets and 6" extension

The procedure (when I say left or right, i mean if you were sitting in the seat looking forward):

Put the front of the vehicle up on jack stands.

Remove the rear skid plate. There are a few recessed bolts that are hard to find, but it should come off without much fuss.

Once you have this off, you will find the O2 sensor on the left hand side, up towards the engine bay from the DPF. As mentioned in my initial post, it's not too bad except that the front driveshaft (that goes from the transfer case to the front diff) is just in the way. You can get your arm up there on the left hand side, but once you do, you can't turn the wrench to remove the sensor. Also, you can't (or I couldn't) find an angle to get my hand on the connector. I tried a 22mm crows foot flare wrench, but found it was impossible to engage it once in place because of the angle the sensor is screwed into the downpipe. I believe that maybe one of those special O2 sensor sockets might provide the necessary clearance, but I'm done buying special O2 sensor tools.

I used my long flat blade screwdriver to remove the connector, and it wasn't too difficult. First I pushed in the detent while pushing towards the front of the car, then I used the blade to push the connector off and it came off pretty easily. Once this was done, I worked on getting the sensor unscrewed from the downpipe. At this point I shot the sensor with some penetrating oil to make my life easier while I figured out how to do it.

What I figured out was that I could get my wrench onto the sensor from the left side, but I couldn't turn it because the angle was too acute. So what I did was put the handle of the wrench onto the right side of the driveshaft (there are also some transmission lines in the way to make this extra-challenging.) The problem now was that there was no room to put any real force onto the wrench handle. So I grabbed the handle off the pump on my press (a regular pipe would work fine, but this is what I had) and used it as a cheater bar to loosen the sensor. Then I reached up and used two fingers (which is all I could get onto it) to unscrew the sensor. My arm got scratched up a bit by rough welds on the DPF and it was uncomfortable, but I eventually got it out.

Putting it together was basically the same in the opposite order, being careful to not smear the anti-seize as you screw it back in. Also, I used one hand to hold the connector and the screwdriver to push it back into place. This was more difficult than getting it out, but only took a few minutes.

So that's it. I've added a few photos of how I did this and the tools that I used. This was a VERY difficult job. Far more difficult than it should be, but clearance is a major issue. I tried removing the driveshaft but it wouldn't budge and I don't know why and just removing the 6 bolts that hold it was a major effort, as they used red Loctite to install them. That's what spurred me into finding a way to making it work without removing it. I am a much better than average home mechanic, I have a lot of tools, and I am one of the stubbornest sons of guns that I know (ask my wife...) I found this to be very difficult, but hopefully all the time I spent figuring out the procedure will help the stubborn amongst us do it themselves.

The light is out and the vehicle is happy again. Good luck to those that attempt it.

Hi Sak,

Good job, you saved yourself 771 euros!
My RRS has been at the dealer since Wednesday with an appointment since the amber engine light came on.
They found the same fault as you just repaired yourself.
It took them till Friday afternoon to finally give me a quote. I noticed the labour hourly rate went up from 89 to 105 euros per hour plus VAT. Almost 20%!!!
With luck, the part is in on Monday.

My question is: what are the consequences of this failure except for the amber warning light?
I think I found that the car didn’t shift up while going uphill, resulting in a higher RPM than usual.

Thanks SW

Sometimes it is not enough to do our best;
sometimes we must do what is required.

2005 RRS HSE 2.7 TDV6
Now: 2016 RRS HSE DYNAMIC 3.0 TDV6

Last edited by SkyWalker on Sun Jan 22 2023 3:51pm. Edited 1 time in total

In general, the vehicle will return poor fuel economy compared to normal. When the oxygen sensor fails, the vehicle will use a default map for fuel delivery, which will not be optimal. This won't usually be a large difference, but sometimes can be depending on how you drive.

For me, just staring at that engine light drives me mad, so it had to be fixed. The vehicle will also fail the annual inspection, so it has to be fixed in this day and age.

And one last thing I forgot to add earlier. You need to "learn in" the new O2 sensor so that it works properly. I did this using my Autel scan tool; if you don't have one you may need to find a friend or pay a local garage to do this. It literally takes 30 seconds, which is longer than it takes the tool to boot up.