Hi Guys,
My 2001 2.5 V6 (UK) has been showing a faulty H2O sensor ( bank 1 sensor 2 or upstream(downstream?), anyway, in the exhaust manifold nearest the bulkhead with the semi-circular heat shield & grey connector?) for a while.

Excuse my lack of precision but there seems to be a variety of descriptions, including left & right, 1 & 2, up & down...

I have checked it and the heater is open circuit, so am pretty confident it is faulty, but it seems to be stuck solid. I've tried to free it, and so have two garages, but it remains stubborn.

It passed the MOT a couple of days ago (after failing initially on emissions and being advised to use 'cataclean' then passed to my surprise!) but is still stuck and now has rounded socket edges and a distorted heat-shield where various failed attempts have taken their toll.

2nd day after the MOT, dipped beam headlamps would not come on. Thanks to Thermo's excellent diagnostics (in a thread back awhile) I bypassed relay R9 #3&#5 and got home - thank you Thermo for your excellent advice, otherwise I was about to call out the breakdown guys!
On further Investigation shows a problem with blown (& blowing if replaced) F67. So,I have two issues;

Any ideas on freeing the sensor &

Given what was likely to be disturbed while they where trying to free the sensor, what is my best bet to try to rectify the short? Looking at the wiring diagram, besides the dip Headlight relay it would appear to feed;
the Active Security Sounder (but I don't know if I have one or where to look if I have)
The Vacuum Module VM1 (front right of the car I think but the without a description or a pic I will have problems identifying it)
Transit Relay? & TCM Relay (pretty sure I don't have one of these tho')

Also, how do I get to the back of the Engine compartment fuse box to access the relay 9 pins? It looks like it should unclip but I wasn't able to work it out how before darkness fell. I have basic kit to splice insulated 1/4" if required.

 

Guy: I'm guessing your stuck O2 sensor is bank 1 (the firewall side), sensor 1 (upstream of the catalytic converter) with a grey electrical connector mounted on the firewall.

To confirm, see pictures of all four O2 sensors and their electrical connectors in this post and the following one: https://www.jaguarforums.com/forum/x...4/#post1084601

Some suggestions to remove this O2 sensor (assuming I guessed the correct one):
+ Cut off the wires to the sensor so you can fit a standard 7/8 inch, 6 point spark plug socket over it. This will grip the sensor better than any spanner or slotted socket normally used on O2 sensors.
+ Use a propane blowlamp to heat the catalytic converter around the sensor. Not the sensor directly, just the metal around the sensor. The idea is to thermally expand the metal around the sensor until it's grip on the sensor loosens.
+ Remove the upper intake manifold. I know - that's a lot of disassembly to get at one stinking sensor. But removing the intake will give you a lot more access to the firewall side of the engine where this sensor hides, and improve the aim of your blowlamp.

As for your headlight, fuse & relay questions, I'll enjoy learning from Thermo's response.

 

Make sure you're removing the correct one as it sounds like you're unsure! The code identifies which one.

 

Hi dwclapp & jagV8,
Thanks for the pics and advice. The O2 sensor is definitely the angled sensor in the exhaust manifold, not the cat, in the pic (#3) is called bank 1, sensor 2. I think this is part of my confusion on the terminology.

I have very limited facilities - lots of tools but no garage or even covered car-port so manifold removal will have to be a garage job, and I'm dodging rain/snow showers at the moment; UK weather is a bit naff currently!

The angle is part of the problem, it seems difficult to get a normal wrench onto it. I have an offset socket and am thinking perhaps using it with a long chisel/drift and mallet?

I'm wondering if I can reverse things? I have a really effective heating mechanism for the exhaust manifold - 2.5 litres worth - and a can of freezer spray - so if I can get the socket on the sensor (possibly cutting and stripping back the heat-shield temporarily?) while cold and get everything set-up before I start her up, get her to temperature then freeze the sensor and give it a tap/Whack..?

 

SiHarvey: The O2 sensor at an angle in the left side of the exhaust manifold is the bank 1, sensor 1 - the upstream sensor, so named because it's upstream of the catalytic converter. These upstream sensors have an electric heating element that with age goes bad, causing the open circuit, like a burned out filament in a light bulb or a bad heating element in a toaster. When it goes bad, the check engine light turns on and the car fails the annual emissions check required in many countries.

Believe it or not, you have more room to access this sensor than I do because US cars have the large power brake booster on the same side as this sensor (since US drivers sit on the left). In UK cars, the power brake booster and driver are on the right.

It's worth a try to heat the manifold by running the engine to get it hot, then cooling the sensor. At least, I don't see how it can hurt anything. Another old mechanic's trick..... After you heat the manifold, touch a bar of soap to the sensor threads where you would normally spraying some rust penetrating oil. Soap melts on the hot metal and, if you're lucky, penetrates the threads. Penetrating oil mostly evaporates when very hot, but soap is a heavier molecule that withstands heat better.

Assuming you free the old sensor, put a dab of anti-seize compound on the threads of the new sensor. Not much, and none on the sensor itself, just the threads.

Good luck, and let us know how it goes.

 

OK, so now I've torn it!

I cut back the heat shield eventually so I could fit a socket onto the faulty sensor at an angle suitable to give it a tap via a chunk of iron bar, and went to start the engine to warm it up.
Lo, she started and ran for about 5 secs then everything went dead. No engine no instruments or centre console, but the locks still worked so after looking at the electrical manual found that fuse 28 fed the ignition switch.

It had blown, and after (unsuccessfully) attempting to access the back of the engine fuse box and wiggling various harnesses, so did the replacement.

So instead of a car that I could drive in the day but had to stop and stick a link in to turn on the lights, now I am stuck with a car that wont work at all!

I have abandoned work for the day (lights getting a bit dim and the sub-zero temperatures are not helping), but would greatly appreciate any advice on how to sort this one!

 

Stupid related thread forum software.