If you have a mystery problem with your car and have already excluded all other potential and most likely root-causes:

CONSIDER A MYSTERY SHORT CIRCUIT!

I am currently working on my X-Type 2.5L 2004. But it really does not matter, which model I am working on - I discovered a general problem, possibly on all Jags?, all Fords, too?, all vehicles?:

I have just removed the air-intake and the cam covers (and whatever else was in the way to get there). As always after removing all those junky parts in a Jaguar engine compartment, I am quite shocked to clearly see the state of the wiring loom:

Everything in the engine compartment gets very hot, which is why they use split conduits to protect the wires. That part makes sense. What does not make sense that those conduits are all quite a little bit too short - the reason for that is possibly that assembly would be too complicated during the manufacturing process if they were longer. This is why one would expect the wires lurking out at the ends of the conduits to be protected at least by electrical tape - and indeed a little bit of electrical tape is being used, but definitely not sufficient: I see the colorful cables being exposed to heat everywhere where they go to the connectors. So either they did not use sufficient electrical tape (maybe to save on labour cost or material cost) or the length of the split conduits simply had shrunk significantly in that hot environment over the years.

ANYWAY: Given that thin wires are DIRECLY exposed to that massive heat in the engine compartment, they will get very easily cracked and loose their insulation here and there. It will be just a matter of time.

I just spend a few hours using up a whole long roll of electrical tape to fix this. AND THIS IS THE IMPORTANT PART: There were two connectors where two wires each just short of the connector where blank already - only just visible - i.e. a little bit of insulation was missing at 4 little cables. Due to the exact location of the missing insulation I just did not have short-circuits there - but that was just a coincidence. But you might guess now where I am going with that: If you are unlucky enough that your car does ALREADY (it is just a matter of time) have a short circuit between 2 critical wires or between a wire and "battery earth" (= any bit of metal on the car) you can expect any type of fault, sometimes permanent, sometimes intermittent. Finding this fault would be like finding a needle in a haystack, especially if you do not expect a wiring short as root cause. You may end up throwing money at your car by replacing all kinds of components without any improvement, because it is not the components, but the wiring, which you would not suspect...


The 2 arrows point to 2 places where the wire in the front has damaged insulation - and not to be seen: the wire in the back also had a bit of insulation mission. I forgot to take a picture of the other connector/wires, where it was even worse.


The arrow point at that ONE wire, which I had not yet insulated properly with electric tape. Before I started this "fix", EVERY connector was trailed by exposed wires.


Close-up, where you can see better all the added insulation tape.

My first job when I started working as engineer in the automotive industry was to figure out how to best do the routing of the engine wiring loom in the Ford Ka. So I understand the importance of those split conduits and the problem it causes, if there is a lack of those at parts of the loom...

 

In addition to my thread above:

Ideally - obviously - one would apply shrink tube, but unless you want to cut the wires to put the shrink tube over them and then re-solder and re-position the shrink tube...: The alternative is electrical tape as above. Sadly, sometimes this electrical tape unwinds itself again. Also: If the damage of the wire is very close to the connector, it would be quite difficult to fix this with electrical tape. Thus, here is what I did meanwhile in addition to the electrical tape, and I might just do it in the future across the board to protect the wires where they are most vulnerable: Close to the connector:

Yet another damaged cable close to the connector...


My new fix additional to the electrical tape: Black silicone (roof and gutter silicone).

Initially I thought about using black heat glue, but since this would melt again in the hot engine compartment, that was a no go.
Obviously, before I apply this silicon I am making sure that there is either none or just one damaged cable - or to put it differently: I am making sure that there is no way that I placed the silicon around 2 copper wires touching each other already.

If you are a perfectionist, you could then apply also slotted conduit (bigger in diameter then the OE conduit) over the silicone - just for the optics.

And I say it again: The lifetime of plastic in the hot environment of an engine compartment is limited (hence the drastic counter-measures). The manufacturer clearly does not care about that as they considered the "lifetime" of X-Type and S-Types to have expired by now. Confirmation of this theory is clearly given by Jaguar's statement that the ATF (Automatic transmission fluid) is in the car for it's lifetime and does not need to be changed. If that it true, the "lifetime" as defined by Jaguar would be around 10 years or more precise: 150.000km at the latest, because that is when an ATF change (full flush with the correct ATF fluid) should be done at the very latest.