Haven't been active here much lately, as summer's been too hot to even think about doing any work, and I spent most of last month travelling. Her Ladyship enjoyed (?) three weeks under a car cover, and survived very well. Although, of course, not all is right with the world and oojah-***-spiff, as Bertie Wooster might say.

So for the past few weeks of driving, I've been getting a CHECK ENGINE warning on the trip meter. The code is FF44, which apparently refers to the A Bank downstream O2 sensor/lambda sensor. The car's running fine, and doesn't appear to be using more fuel than normal (difficult to tell, as I haven't had much time to get out of the city, but she'll still do better than 20 mpg cruising on the flat at a steady 80 kph or so).

At first, it was more or less random when it would show, both from cold and warm. Now, it shows within the first few minutes of starting the engine up, but only when the engine is fully cold (after a night). Coming back, even after several hours in the carpark, it usually stays off, even for an hour-long drive through the hills.

It's the trip meter warning only--no "Check Engine" light on the dash. I check the code each time, and it's always FF44. I experimented with disconnecting the neg. terminal for a moment--that cleared the CHECK ENGINE that showed when the key was in Position II, but it soon reappeared after setting off.

The fact that it appears these days just around the point I'd imagine the initial cold enrichment period ends, and doesn't (usually) appear when the engine is warm, suggests it's not a loose connection but a failing somewhere. However, I would like to check connections. O2 sensors do, according to some comments I saw, fail enough to be considered wear items, so it shouldn't be too hard to replace... I hope.

The problem is, I have no idea where the bloody thing is hiding! I've done image searches, which show me the O2 sensor on a bench, or in other cars, or (in the case of Jaguar Classic Parts) as a diagram unrelated to anything else. I believe it's somewhere on the A Bank exhaust manifold, but an extensive hunt this morning has failed to reveal anything that seems right. There is an empty screw hole at the top end of the starboard (A Bank) catalytic converter, but that wouldn't be it... would it?

Location of mystery thread on cat.

Any advice about where to hunt would be much appreciated. As, of course, would any advice on the issue in general....

 

I would look for it at the downpipe. Here is a random V12 downpipe w cats, it seems to have lambdas before and after the downpipe cat

Ebay V12 downpipe

 

Hi Someday

No more than an educated guess (ish!) but I think the O2 Sensor is on 'B' Bank just past the Exhaust Manifold, so you could try looking there

 

Leo - so the open screw threads on that cat are where two O2 sensors go? That was where I was looking, and the upper one of those is the photo I added to the initial post. But surely a completely missing sensor would be a little more than a suggestion from the car to perhaps check the engine...?

OB: According to this thread (and others) FF44 is a right-bank/A Bank/starboard bank O2 sensor code. I'm assuming of course that "right" is always "as seen from the driver's seat" or in other words, starboard. According to this other thread, " On the exhaust on the right side, if you turn the wheel to the left, you should see the sensor screwed into the exhaust pipe." So I did that, steering wheels turned hard left, had a look, and couldn't see anything that looked like a sensor.
I have found a suggestive photo here, however--but it's on the left side, and while I checked that, I didn't notice anything like that.

I am quite puzzled....

 

Hi (Some Day)²

Google tells me that the thread size for these sensors is M18x1.5. I will say the threaded hole on your picture looks a lot smaller, and so do the bushings on the EBay listing I linked to. They do also look too high to allow the sensor end to protrude into the gas flow.

Still: The sensors must be placed in the downpipe near the catalysts. On the AJ6 engine in XJ40 the position of the sensor is on topside of the downpipe close to the olive joint. Not easy to access !
The AJ6 has 2 metallic converters before the O2 sensor and 2 ceramic catalysts placed in the intermidiate pipe under the floor

 

Thanks again, Leo. Much appreciated. I'll take another look tomorrow when it's daytime and see what I can see in the area above the catalyst. If that photo I linked to is the same as on my car (which it may not be), then that gives a hint (though I don't know if mine is laid out quite like that). Jaguar Classic Parts suggests or hints that the Japan-market exhaust system has some differences to ROW, so it might not be that easy. We'll see. Or, rather, I'll see....

 

Hi Someday

If that Photo is showing the Passenger Side on a RHD Car, then it is on the 'B' Bank Side

Maybe its different on Japanese Cars but it seems to be in the right area or should that be left area

And it was only a 'guess'

 

Thanks OB. The photo I took, in the first post, is the A Bank (starboard side), where the FF44 should be coming from according to what the FF44 code means (I think FF45 is the B Bank). The linked photo, not mine, is the left side of what seems to be a US car, but if the V12 has one on each side, the locations should be the same. Should be....

 

Well, I took another look this morning, armed with all this knowledge, and found the O2 sensors, on both sides. The O2 sensors are located on the inner sides of the downpipe just before the cat, and hence are essentially inaccessible without getting under the car, something I'm deeply paranoid about even with jacks. I could possibly unscrew them, but not do anything more than that, and I was utterly unable to trace their wires to wherever they might connect, which makes it hard to determine if the issue is merely a poor ground.
Might just order a new one (new two? Get both done on the assumption that if one fails, the other's not far behind?) and get the garage to do it, with their proper lift. And someone other than me under it....

I did manage to locate the engine earth strap sub-chassis attachment, or what I'm 98% certain is the engine earth strap sub-chassis attachment, and while a bit greasy and dirty, it looks pretty clean.

 

Info for a North American TSB for later cars. Might help??

bob

 

Thanks, motorman. It's certainly suggestive, and worth cleaning the grounds now I know which ones to clean. The starboard bulkhead ground boot on my car has hardened and cracked, so the ground connection there might be less than ideal.
I was wondering if it wouldn't apply because the FF44 warning (generally) only appears when the engine is cold, but as it's a heated O2 sensor, it would also only (generally) appear when the sensor is cold.

So the supplementary grounds need only connect the bulkhead and the intake manifold, not the actual sensors. That sounds much easier....

Oh dear: from page 12 of that PDF we get this: "...increase your vehicle's emission system performance and enhance it's reliability." Sloppy, Jaguar. Very sloppy.

 

Mystery hole on the converter is for exhaust temperature sensor, Japanese specification.

 

Thanks, xjsV12. That's odd. In that case, as mine is Japanese-spec and has am exhaust temp sensor (which has shown up once or twice), it shouldn't be a hole. Hope it's not missing or anything. Very useful thing, that is.

 

And also all exhaust pipes is covered heat shields. Perhaps this threaded hole is for heat shields.

 

You mean the grass shields? Could be. In that case, they're missing. There's signs in one hole that something might have snapped off, actually. I need to examine further. Ideally find a photo or reference of a car with them on. I've not noticed one before.

I also need to re-read that TSB, as it seems to tell me to connect secondary grounds to the intake manifold, which is aluminium. Not a great conductor, I believe.

Today, just to confound matters, the check engine warning didn't show at all on the way to work, when the engine was cold, but did halfway home when the engine was warm. The starboard bulkhead grounds are looking rather grotty, so first thing is to give them a good clean.

 

Yes, it looks like you're right. I'm missing my heat shields. There's a good photo of one of them on this page (all in Japanese but the photos are clear) about replacing the O2 sensors. Hmm. Why are they missing? Hmmmm..... And how important are they?

 

I think they are important only for technical inspection (MOT). And for grass!!!

 

Well, my car got through the Japanese MOT just a couple of months ago, so not a worry here I guess.
And I don't do a lot of off-road parking on tall dry grass, either. So I might just leave them off for the time being. Especially as I suspect the reason they're not there is because at least one of the bolts may have rusted into its hole and snapped off.
Here's the photo I took using a probe, which is why the quality is so low.

Snapped-off heat shield bolt, methinks....

 

Hi Someday

What sort of probe did you use to take that Photo, as methinks it looks a lot better than some of my Holiday Snaps

 

Ha. I bet it doesn't.
It's some cheap Chinese borescope I got on eBay for chickenfeed. Connect to your tablet or phone and use an app that sends secret government spy data to the CCP, and you can see in the awkward parts. If they're in focus. In this case, frankly, one of my wife's small mirrors and a torch worked better....