Afternoon. Kind of at my wits end with my X-Type. Starter locked on me 2 years ago. Replaced it. Things seemed okay. A year later, the car would only start in fits. I didn't have the time or money to look into it much as it was my only car, so I bought a Ford Escape beater to get me buy for very cheap. Periodically, over the past year, I have tried to start the Jaguar. Sometimes it fires; sometimes it does not fire.

Weird things:
-The car has a hard time maintaining an idle until it has ran for a good 5 minutes.
-Sometimes(especially after driving for a while), the booster just seems to lock? My brakes get very hard.
-When using the turn signal, the top brake light over the back window blinks as well.
-When using the turn signal while in the run(but not actually running), the shifter clicks every time when you switch the direction of the turn signal.
-The powered spring door thing that is in the front of the air intake likes to constantly click or whine(has been replaced with the same results)
-When turning the key to the ignition phase, you can hear a pop or click coming from the fuse box(specifically, the relays)

Things I have tried:
-Disconnected battery for long durations. Sometimes, the car will fire up; sometimes it still does not.
-Ran a instrument panel test(holding the trip button). I see the odometer change to "gage" with some clicks then nothing happens. I can cycle through a BOATLOAD of codes?numbers? for a long time by pressing the trip over and over.
-Unplugged and plugged the ECU
-Ran a $1000 OBD II computer on it. It threw about 60 codes all over(thus, I think a bad ECU?)
-Replaced the 12v40A relays at the fuse box(one old one was rattling)
-Tried most of the above while on a jumper as well(just in case)

Notes:
-The small led at the shifter turns off after a couple of seconds or so with the key in the on position thus, the security system should be fine.
-Whenever you press the brake pedal, the headlight indicator comes on the instrument panel.
-When you press the brake pedal and use the turn signal, the panel indicator for the turn signal goes double speed.
-When you turn the key to ignition, you can ALWAYS hear the full pump coming on and staying on.

Just looking for any other things to try or advice. I am okay if the ECU is trashed. I can get one cheap and should be able to get it programmed for cheap. If it is a instrument panel, the car goes.
I've had the Jag since summer of 2018. I really enjoyed driving it as it was a AWD model. It got decent fuel milage and was just a blast to take on the highway.
When the car does start, the motor and transmission still feel as good as they did at 130k miles as they do now at 199k(always keep up on maintenance).

 

So many weird issues and odd light indications.....
If it were just a weak cranking, then corroded battery cables (inside insulation) would be the direction to head, but those other issues seem more like earthing type problems.

Check battery voltage, as anything under 12.6v at rest is likely to be a weak battery and will stuff up the electronics with phantom issues.
After that check you do not have some faulty earths......... under the dash serves the instrument cluster, climate control etc, for J-Gate near drive tunnel and A pillar earths for TCM etc.
Download the schematic for your year as it shows the various earthing points for you to check and clean.

 

Seeking, if you find the car hard to start, try turning the key to the RUN position (DO NOT take to start), let it sit there for a few seconds and then finally take it to START. If you find that the car starts easier, then this is a sign that your fuel pump is starting to go. It is very possible that a weak fuel pump is causing a lot of issues. The other thing I would look into is when the last time the fuel filter was changed. I have seen a lot of strange starting issues be resolved with a new fuel filter.

As for the strange light issues, a lot of this can be attributed to bulbs in the back of the car not being installed properly and they are shorting between contacts, resulting in erroneous lights coming on.

The other thing that I would look into is the wiring harness in the back corners of the engine bay. LIttle critters like to crawl up there and eat the wiring. This can lead to all sorts of random issues as they love the vegetable based wiring insulation Jaguar used as food and this will cause wires to short together and cause who knows what.

 

I think I was misunderstood as to what the problem is(my fault). I do not get a CRANK. When the Jaguar doesn't fire up I mean that it is not cranking/turning over. My bad.
Having said that, I reseatted a bunch of relays, yanked some wire harnesses, etc yesterday.

The car turned over and started. However, now the car is running at an extremely high RPM (3000). So, it would appear my connections or cables are loose somewhere to get the starter to turn. But, even when I fix that, I now have an idle issue/RPM issue at idle.
If I put it into gear, it stays just as high with the RPMs.