Kim reported a new engine light on today, so I went out for a look.




I guess the above figures were during warm up first thing this morning so had a look at the trims when warm this evening.




Does anyone know if the 4.2 part number for the post cat sensor?

 

OK I found it, Oxygen Sensor - C2C25956 | Jaguar S Type, Jaguar XJ - X350 - XJR, Jaguar XK8 - XKR | Jaguar | British Parts UK

Ill check the resistance if it ever stops raining here.

Has anyone successfully got this one out from the top of the engine bay?

 

I just had a look and tested the sensor, its heater is open circuit. It looks pretty much impossible to access from the top, I'll get one ordered and try to fit it from beneath at the weekend.

 

I bought this sensor from ebay and set about this job this morning, it took about an hour all in.


4-wire Post-cat / Downstream / Rear Oxygen Lambda Sensor for some Jaguar models | eBay

Access to the lower sensor from below is very restricted, the gap between the transmission and exhaust is only about an inch and a half.


This picture gives the wrong impression of how bad the access is.





Access was done this way with a wobble on the O2 socket and a couple of extensions.





I first tried it with a 3/8th set up which ended in failure.





So I moved on to 1/2 inch which was able to break it free.





I was able to reach down from the top with my skinny arms to screw the new one back in then tighten from below.


Job done.

 

Ended up working on this, too this past week end. Followed this thread, managed to put the split O2 socket on the sensor with a long extension, as pictured above. Applied torque, and the socket slipped a couple of times, sensor stuck. Sigh. Moved on to the split crows-foot socket, same thing. Figured I better stop and get better access before the sensor was completely rounded off.

Now, on to removing the cat. 4 bolts on top: a little tight, but came off fine. 2 bolts at the bottom: fine. 2 bolts on the bracket with the trans: fine. 2 bolts with the exhaust pipe: took a lot of umpff, but came off fine, too. Now, trying to get the cat off. Not enough clearance. the studs on the cat are LONG, how am I going to get the exhaust to move back? Called it a day.

Well, "sleeping over it" worked this time. The key is to disconnect the exhaust pipe from the cat on the OTHER side. Once the exhaust is off BOTH cats, it can move back enough to allow the cat to drop off.

From there, smooth sailing: Used a 22mm box wrench and a hammer to get the sensor off. The whole thing was on a pile of towels to try and minimize the damage to the cat internals. I checked the internals from all openings, and it seemed fine, no loose piece, all light grey. I suppose a big expense saved right there. Re-assembled the whole thing with anti-seize paste on the threads. Plugged the O2 sensor harnesses back in, put the connectors back on their posts, and put the intake pipe back on. Then on to a hard reset, and OBDII reset as well. Time will tell is the tests pass (P1000 for now). The MIL light used to come on immediately after a reset, but for now, it is still testing, MIL off.

In short, more work than I expected, but not too bad overall. This is with the front of the car on ramps, so not a lot of clearance.

Part: DENSO 234-4798 Lower Oxygen Sensor

 

Too bad you had to remove the CAT, here's my adventure. Read to the end for the final results.

https://www.jaguarforums.com/forum/x...rs-how-149326/