Hoping someone very smart and knowledgeable with X350's can chime in here -

Since 2018 I've been in possession of a beautiful blue Jaguar XJR from 2004 here in The Netherlands. The car has been fantastic, even through all the things which have broken throughout the years, and still drives great. Unfortunately there are a couple of electrical gremlins haunting the car during my ownership which I have been unable to sort out. Hoping someone here can maybe correlate the issues I'm having and tell me where to further advance in my diagnostic process!

Current issues with the car:
1. The battery drains relatively rapid. Battery has already been replaced, this wasn't the issue. There seems to be a big electrical load 'peaking' on the battery, which causes temporary voltage droop and of course discharge.
2. When parked and locked the car flashes it's hazard lights at random moments for a brief second
3. The car is equipped with front passenger seat control from the rear right seat, this does not work anymore.
4. There are a couple interior lights broken
5. Once every one to two months the car does not start due to the PATS system immobilizing the car.

1. Battery drainage:
The car's battery lasts about 5-6 days before reaching less than 12.1 volts. It does this in peaks, where the car battery is initially 12.8 volts, then drops to 12.5 volts and then back to 12.75 volts. This makes me think that there is an electrical system causing issues in the car. I almost always keep the car connected to a CTEK MXS 5.0 trickle charger to mitigate the issue with drainage as a temporary solution. As you can see in the graph at 2025-04-03 -> 2025-04-07 it drains a 100Ah battery for 50% in 3 days (from 12.8 volts to 12.4 volts). During this period it was not connected to the CTEK charger, the other dates in the graph it is. The weird thing is that sometimes the car does not drain for three to four days (only loses roughly 0.05 volts a day), but then decides that it's going to drain anyway and you see the behavior shown below in the graph. I've replaced the battery and can say with certainty that this was not the issue. The old battery from the Jag is functioning well in my BMW E91. The battery model I've used so far is the Varta H3 100Ah Silver Dynamic, 830A, 12V. Other models/sizes would drain even quicker than this Varta.



2. Car flashes hazard lights when parked at random times.
When the car is parked and having it's drainage issues, it also randomly flashes the hazard lights for a brief second. It does this maybe once every 15 to 60 minutes. Hard to exactly register.

3. The car is equipped with front passenger seat control from the rear right seat, this does not work anymore.
Both seat controls front and rear work perfectly on their own seat. Only controlling to front seat from the rear right seat does not work anymore. It did work in the past.

4. There are a couple interior lights broken
Rear right passenger seat light, rear right passenger reading light and maybe one more somewhere. Not sure if this would cause one or more problems.

5. Once every one to two months the car does not start due to the PATS system immobilizing the car.
I always lock the car with "double lock", where it beeps and folds the mirrors as well. I've uploaded the symptoms in this video:

You Tube

You Tube

This problem and the drainage problem are probably the most annoying ones. I've been able to read the codes its thrown during a period of immobilization, please see images attached below for codes.
When the car does not start anymore it's unable to do the following:
a. Unlock all doors with the remote, usually only the drivers door is opened (or not and it has to be opened with the physical key)
b. The electrical mirrors do not fold out
c. It throws errors with "steering column locked" and "parking brake defect" in the instruments cluster.
d. The PATS lights flashes rapidly, there is no crank.
e. During the attempt to crank at least the climate control system and infotainment shuts off.

The solution to the problem above is to disconnect the negative battery cable in the trunk for a couple of seconds. After reconnecting the anti-theft alarm immediately goes off, but is able to be silenced when pressing the unlock button on the keyfob at which point the mirrors unfold themselves and the other doors unlock as well. The car then returns to its normal state for one to two months without noticeable issues.

I feel like there is something weird going on with one or more of the electrical modules. Might be a bad ground connection somewhere or a pinched cable. Car does not throw any errors when driving. I've also confirmed the battery drainage by putting my Brymen BM869s multimeter in between the negative battery cable and the battery in order to rule out a defective Bluetooth battery monitoring device I use to keep track of the car's voltage. Was unable to measure any voltage drop across fuses, because the drainage problem only happens in spikes and is not consistent. Also it usually does not happen for the first couple of days when the car is initially parked and locked. I just don't know where to look for issues anymore... Appreciate anyone who can help me with extra insights!

If it can be of any help, please find attached below the SDD DTCs during issue '5' where the car immobilizes itself.

For the drainage, normally you try to find the circuit that has the drainage by usinf an Ampmeter and pulling the different fuses. If the drainage drops with one specific fuse pulled, then you have found the faulty circuit and can investigate further in that circuit. The problem wit these cars is that after switching off the car, the control modules need up to 30.40 minutes to go to sleep, so that you can only check the drainage after this time, with the modules active you will not get a relialbel reading from the Ampmeter. Also, some of the modules "wake up from time to time. Unfortunaltey, I don't have any other solution at hand.

Regarding the non starting of the engine, the immobilizer is a different circuit from the alarm system that gets activated via the key fob, and normally an active immobilizer lets the engine crank and start, but it will die immediately. In that case, more often than not the culprit is the receiver next to the ignition barrel that should receive the signal from the transponder in the key fob.

Best regards,

Thomas

Hello Thomas,

Thank you so much for taking the time to reply!

1. It's indeed challenging to measure the drainage, especially since it does not always occur and when it does there is a big current draw for a couple of minutes. By the time I've been able to measure all the fuses in the trunk and engine compartment (not even considering that impossibly located interior fuse box) it's already gone. For this I locked every door/lid manually, so that I was able to access the insides even though the computers thought it was locked. Unfortunately after a lot of testing, checking interior systems for moving parts, sounds and lights possibly staying on, my investigation yielded no results. I think the only option would be to utilize SDD to further diagnose if there are modules waking up or causing system-wide mayhem. Unfortunately I only have access to a (presumably) unofficial version of SDD V130 with a crappy Mongoose clone cable. Trying anything big such as service functions or programming with the combination of the two is a recipe for a disaster. I did read something on the forums about being able to read how often a module wakes up and possibly more, but have unable to find this function in my version of SDD. Also some functions don't seem to work and just take me back to the homepage, or crash the SDD software.

2. Thanks for this useful insight, but this also confirms my suspicion that there is something funky going on with one or more modules causing a system-wide communication problem. Especially considering that a lot of the codes thrown should result in big problems when trying to drive the car, which is not the case. I'm afraid something is messed up in the wiring or a module and I feel like a couple of these problems are related to each other (drainage, flashing hazards briefly when locked and failure to crank/lots of errors).

Anyways; maybe someone else here on the forums can shed some more light in the best course of action for ruling out problems. So far I have the following suspicions:
a. Problem with a ground/short in the car somewhere causing too low of a voltage causing modules to be confused.
b. Something wrong with a power distribution box, sticky relays or something or maybe a missing fuse? I'm pretty sure that the drainage issue was already present when I bought the car, but didn't really notice it till covid.
c. A module such as the FEM/REM not functioning properly anymore and causing communication problems on the networks in the car. https://www.jaguarforums.com/forum/x...-drain-226289/

If the conclusion is that I have to purchase a genuine Mongoose Pro cable (but where do I get the proper software?) or a proper OBD-II scanner for further identifying problems, then of course that would be the next step. I've read a lot of information about which is supposedly the best clone cable or software, but also read so many horrible stories about dead Jags after messing around with improper SDD setups, or failing to connect a quality power supply during programming. Even my own Jaguar mechanics, specialist shop where the car is maintained, have told me that they'd rather not perform programming on any cars due to a bad experience once. They still have a very old Jaguar IDS system from 1998 for diagnosis and programming.

Once again, thank you (and everyone else here on the forum) for your time and thoughts!

Best regards,
Felix

I suggest that you need to check for a parasitic drain which
you can do easily by connecting your multimeter in series
to the negative side of the battery.
If you can record the readings then even better.
Something of the order of 50 ma is ok.
If you find an exessive drain say 250 ma or more
you need to trace it by checking for voltage on each fuse
and you can do that withoiut having to remove each fuse
and finding a very small metallic area on the top of the fuse.

Do a hard reset which may clear away lots of your DTC's
Do NOT use double locking

The easy part is that most all of the faults you show are triggered by low voltage. With that many it would most likely be less than 11.8v during a start attempt. Use SDD to clear the codes and immediately read the codes again. Watch your battery voltage while doing this. Mine will throw codes with a battery at almost full charge, during an SDD test, since it can draw close to 50 amps during the test.
The car runs a self test at regular intervals. If it sees a fault it may not go back to sleep.

Looking at your profile you’re based in The Netherlands. There are two options for you: G&G or Werkman.

I feel with you, I had similar issues with battery drain during my early ownership of the car.
My analysis at the time showed that the car when being parked would randomly power up its electronics which then would eventually fall asleep again with time like after a regular stopping of the car. When you park and lock these X350s they take about 30 minutes to put the last electronic module to sleep, and in the meantime the slowly dropping number of modules consumes a considerable amount of electricity.
Due to lack of a proper measuring device with logger I checked the issue by disconnecting the ground cable from the battery and reconnected it via a multimeter. I then set my digital camera to shoot one picture every minute, pointed it to the multimeter in the trunk with a little tinkered support and locked them both in the trunk over night.
The resulting time lapse movie from all the nightly shots showed that the car would wake up to three time per night to about 2A consumption and then in steps slowly drop down to almost zero again over more than 30 minutes, the residual minimum amperes probably around the level that the dashboard clock takes.
Do that consistently over 2 to maximum 3 days and the battery is dead (after all a lead acid battery can only use about 20% of its nominal capacity without taking increased wear or damage).
In my case I couldn't solve this myself, so I eventually gave up and brought the car to Jaguar Classic in Essen. They solved the problem, but unfortunately they never revealed all the details they had done. They had however found a totally messed up wiring of the OBD socket under the steering wheel and changed and rewired that to a new one. As there were no more related material costs on the bill I'm sure there were no electronic modules or other hardware exchanged. And since then the green beast will always start, even when it stands for a week or two.
Of course this doesn't mean it's the same issue on your car, but I had also experimented with other used REM or FEM from ebay, and that had no effect in my case.
I think I had written the story of my electric leak somewhere here in an old post also with pictures, so you might find it when searching.

Wish you good luck. I know how frustrating it is to issue a first short prayer every time you push the key FOB, hoping the car still has enough juice to at least open, and then a second longer one when you turn the key to start 😊

That is a very interesting and wondering info.
I have read your two older threads on the issue:
https://www.jaguarforums.com/forum/x...urrent-195972/
https://www.jaguarforums.com/forum/x...ce-rem-220474/
And then, the issue solved and apparently due to an incorrect wiring of the OBD socket. Very surprising! Could it be so from the factory at the time of delivery or later on due to some improbable OBD socket replacement?
Or could it be that Jaguar Classic actually replaced a faulty relay or other uncostly item using a spare piece?
Btw, I could not read the video that you posted, maybe corrupted: JagRuhestrom.avi
This kind of issue is most worrying because of the difficulty to understand/trace all of the components consuming power before going asleep, especially if one of them starts becoming rogue...

I found another very informative thread on this topic here by member matsd, who also had similar issues which came down to a broken wire around the FEM.

X350 waking up frequently

I somehow remembered this post, but couldn’t find it right away.
Very interesting read, but also showing that the issue can be in a lot of places. After all these cars have many kilometers of wiring

Sorry for that. That was an avi created by the digital camera from the individual multimeter pictures overnight that were taken every 60 seconds. Seems to be a strange format, I can’t open it myself anymore. If I still find it on my PC I try to recode it to something working.

Have you seen the Jaguar "VEHICLE QUIESCENT CURRENT TESTING" document? I have attached it. Gives some current drain specifications for different Jaguar models.

I don't use the old fashioned method of putting your meter in series with the battery cable to measure current draw. One it's real awkward and you will be always waking the car up so you need to start all over again with waiting for things to go to sleep. But the worst thing is it exposes your meter to potentially high DC currents that can burn the meter out or pop the fuse in seconds. The better meters like Fluke will have re-settable circuit breakers to protect them.

That can't happen with the clamp on meters. Plus again the ease of use as you can rapidly go from wire to wire without disturbing the car. You do want one that can read low ma DC currents as that's what we are looking for.
I use this GTC meter as it will measure down to 1 ma DC. It's a GTC CM100.




But there are others that should work just as well.
It can be a big job and I have spent hours tracking down current draws.
.
.
.

Yes, you are absolutely right, the method with the regular amp meter should have had some disclaimers:
- don't even thing about getting close to the ignition lock with the key with the meter connected
- don't even move the electric seat
- no lamps, best leave the doors closed to not even trigger the interior lights
- at best don't do anything that consumes electricity beyond the boot light and door locks
the usual 10A tolerance of a regular multimeter is exceeded very quickly. I was at around 6A directly after connecting when I remember correctly.
But like probably most, I don't have such a nice DC amperemeter lying around

Hello everyone,
Once again thank you all for the extensive research, referring old forum posts and thinking outside of the box. I haven't had the time to further investigate, but have just picked up the project (at a slow pace) once again. So far I can confirm the following:

1. The earth points G1, G2 and G3 at the front of the engine bay had severe corrosion and eventually the headlights (HID, Xenon) stopped outputting light for a brief second when driving over speed bumps. This issue has been resolved by my Jaguar specialist and I'm glad I didn't try it myself. During their work the earth points snapped off and had to be fully repaired. Haven't yet looked at them, but I've been told the issue has been resolved.
2. The drainage issue still persists and at the time of this original post (April, 2025) I put my Brymen BM869s multimeter in between the negative battery cable of the Jag and the battery itself. I measured twice for roughly 12-16 hours via an optical datalogger on Windows, connected to the multimeter of course. Once when the battery voltage was at it's max (12.8+ volt) and once when it was lower (12.6- volt). This yielded in the following results:

With lower battery voltage the car experiences HUGE peaks in current while it should be asleep. These peaks can also be measured via my external bluetooth voltage monitor which I have installed on the car battery. During such peaks the car's battery voltage drops by a large amount (e.g. 12.5 volts to 12.25 - 12.3 volts). Of course these peaks can also unsettle the stable module thus resulting in lots of logged error's. So far I have focused my attention on: "B2496: anti theft horn output circuit short to ground". As far as I understand in the electrical diagrams this is connector EC36-20 (FEM / Connector EC36 / Pin-20). The FEM is able to activate the "horn relay circuit" by switching to ground. The horn, which is actually a dual horn system, is on a LHD car like mine located at the left front wheel near the bumper. The horn itself is connected through ground point "G1AR" (which was severely corroded). The FEM can call upon the horn circuit in case the alarm system is activated. Hmm...





I haven't yet been able to run SDD on the car now that the ground point should be fixed, but according to my wireless volt meter the issue is still present. I disconnected the trickle charger and low and behold the car almost immediately broke itself and all electronics froze - due to the voltage drop caused by running on a healthy battery at 12.8 volts instead of 13.5+ volts of the trickle charger @ 5A. It then showed the exact behavior (no central unlocking, no crank, etc.), but battery drainage was only 0.05 volts per day. This is interesting information, because it probably means the issue is purely related to electronic issues (e.g. modules powering on circuits when they shouldn't), instead of physics problems such as a bad/defect diode in the alternator for example. The main suspects are the FEM/REM who also control an additional switched power supply circuit.

I've also confirmed that the battery backed sounder for the security system is working correctly (located in the wheel arch / liner at the rear right wheel). This seems to be a common issue on older Jaguar's (XK100, X308 and below). Of course I won't be entirely sure if there isn't any corrosion or other shenanigans, but the alarm goes off if power is disconnected and the beeper also beeps if I lock the car with an open door. Functionally they seem to work as expected.



Currently I'm out of ideas how to further proceed with investigation. I have pulled fuse F25 (Horn circuit), which should have made the horn circuit non functional. If there really is a short to ground causing issues, then this should yield in interesting results. Athough the short might be solved now that the earth points have been fixed. My gut tells me the most logical step to proceed is to either physically inspect the FEM for possible corrosion and start measuring pins, or by utilizing SDD to find interesting information about the wake-up statistics of modules, possible voltage issues etc. If it really is the horn circuit causing issues somehow, then the car really told me what the root issue was via it's computer system all along. All the other SDD DTC codes are presumably due to low voltage or noise on the SCP-network. I feel like the short circuit B2496 is a valid DTC which shouldn't be ignored or caused by low voltage.

Once again, thank you all so far for taking the time to write extensive replies and sharing your own experiences/thoughts!

Many (most?) 'short circuit to ground' faults are caused erroneously by low voltage. I would not worry to much about the B2496. Even if it is an actual fault the draw should be small and consistent.

Just for the heck of it jumper your hood/bonnet switch and see what your voltage/current does over a period of time. They can be intermittent and keep the car from sleeping properly.