2005 XJ8, 82k miles. Everything worked perfect on car until today. Then discovered the following items inoperable: Headlights, washer/wipers, power windows, front side markers and turn signals, glove box and trunk release. Note: All rear lights working including turn signals, outside trunk release and remote locking.

Battery is relatively new, cables clean and tight. I removed/cleaned the ground cables in boot and behind the headlights even though all were clean and tight. No luck. Suspecting bad FEM since all problems seem to be in front half of car. Tried a search with no luck, any ideas?

 

Hopefully not as catastrophic as you might think.
Check your earth grounding studs. The aluminum body suffers from earthing stud failures.
Known for corroding and breaking away creating odd behavioral errors due to poor earthing of systems.
Grounding studs behind headlights and in engine bay would be the place to start.
If you download an electrical schematic PDF of your car from JagRepair.com - Jaguar Repair Information Resource it shows where all the different grounding points are located.

If you have a bad stud, you can simply drill and replace with a suitable sized stainless bolt and nuts.

 

Hi Andyzjag,

is it only the front power windows that do not work, or all of them?

If it's only the front ones, and as you state that you have already checked all the earthing points, I would also suspect either the FEM, the Front Power Distribution Fuse Box or partly the Passenger Footwell Fuse Box, as in the fuse box there are some relays that can fail. Officially, some of these cannot be replaced (Jaguar calls them "non serviceable PCB relays"), but in fact they can, but with a lot of work.

The "how to" was shown in this thread:
https://www.jaguarforums.com/forum/x...-issue-166742/

Unfortunately, you cannot just swap the FEM with another one, you need to configure it to suit your car with SSD.

As the FEM is also difficult to reach, I would suggest to check the fuses boxes first.

Best regards,

Thomas

 

This should be the schema I suppose:

 

Yes without using SDD you can't see far enough into the car.
And as posted above even IF it's the FEM that also requires SDD to program.

Do you have the electrical guide for your car? If not I think you will want a copy?
I have a copy but again and again the forum limitations prevent me from uploading it?
It maybe in the sticky at the top of the forum under the "How To" section? There is a ton of good stuff in that thread.
With such a massive failure I wonder if one of the Mega fuses burnt in two? They are all listed in the electrical guide mentioned above.
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Hi, thanks all for replies and the ground point diagram. I don't have the electrical guide but sounds handy. As mentioned in post, I did check and clean all 3 ground points behind headlights, as well as those visible in the trunk. No culprits found. Yes, all 4 windows inop, along with other items mentioned. Bonus item: Fuel filler release inop, so no way to add gas. 2nd Bonus item: Glove box release also inop, so cannot access glovebox. I agree, multiple systems out so suspecting one of the mega fuses. Can you point me to their location? Thanks, Andy

 

Not a solution much but when I was doing stuff under the steering column I noticed a hole with a symbol of a fuel filter flap and the word RESET. The hole is to the left of the brake pedal. I did not look into the manual what does it do.

 

Why are people saying "analyse with SDD", when that number of issues all at the same time, suggests something un-analysable, such as a common-ground problem or connector problem.

Does SDD analyse ground problems and connector problems?
Just asking.

 

Here's a link to download an electrical schematic for a 2005
http://www.jagrepair.com/images/Elec...al%20Guide.pdf

Doing a quick trace back of a number of your faults, they don't all appear to trace back to a single mega fuse, but nevertheless it would be worth checking both the 175A and 100A fuses are still intact which are located in the trunk near the back of the battery. There are three mega fuses in the power distribution block, the other one is 500A.

 

You can find the electrical guide here in the forum, together with the workshop manual and lot's of tips:
https://www.jaguarforums.com/forum/x...enance-246865/
Youl will find all fuse box locations in there.
The fuel filler cap can be released manually, but you need to remove the right inner lining in the trunk.
If all 4 windows are inop, then the problem will not only be the FEM, because the REM is also involved in that.
Best regards,
Thomas

 

Mega fuse failure very rare and fuse box failure more common
I suggest that you buy an used fuse box and try it
Ensure that you get the right one
eg
https://www.ebay.com.au/itm/12508777...4aAkKYEALw_wcB

 

Can't this be diagnosed somehow before ordering the replacement part? 😲

 

ChrisMills to answer your question about checking grounds?
Yes SDD "can" do that BUT it requires another bit of kit as our UK friends say.

So SDD has a built in way to measure voltages, current, resistances, pressure and vacuum. Plus full oscilloscope functions too. Even stuff like vibration analysis used when looking for NVH problems. And a drive shaft balancing section. They called that device a VMM (Vehicle Measurement Module). No mention of checking grounds but I think that's included with all the other measurements?
I have never heard of anyone at least outside of a Jaguar dealer who had all the required equipment either?
I was very interested in this added function but came to a dead end on how to do it? I just looked and used VMM's are going for $1200-$1500 on EBay so I guess they are out there? Just remember this is in addition to the cost and complication of a SDD/Mongoose setup.

I have attached a document that talks about an earlier version used on Ford products plus JLR products.
Also a document with a system description showing all the functions available.

You can see in SDD where it is located from this screen shot from SDD. You must open a measurement applications type session. Which is not the same session you use normally when troubleshooting the car using SDD.




Can anyone add anything?
Has anyone used this function or has a VMM?
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Thanks everyone for suggestions, I was able to access the wiring diagrams for this car in the sticky note section. After studying the wiring diagram, it looks like the multiple failures do point to the front fusebox (FEM). I have not yet checked the 3 mega fuses in the trunk. The middle mega fuse (175A) feeds the front fusebox but the FEM is reading source voltage at several fuses including its mini- mega (90 A) fuse, so I'm not suspecting the mega fuse. I am planning to remove the FEM and check for anything obvious before I try to source a used one.

 

By the way, the FEM is not the front fuse box. The FEM controls a whole lot of stuff with processors, the front fuse box is just fuses and relays.

Front fuse box

Front Electronic Module

Pete M

 

Good catch, thanks Pete.

 

Ok, solved it. It was indeed the front module (FEM). I was able to source a used one on eBay with no problem. The part number for the replacement module had a different two letter suffix than mine, but same year (2005). It was plug and play (although there are a total of five plugs so required some fiddling). But no programming, and all systems working again. Thanks for everyone's help, now just need to find and fix that clunk in the front end.

 

Good to hear that you were able to fix it!

Regarding the clunking noise in the front, I also had one on my car. In my case, in the end it turned out to be the front sway bar bushings, which means cheap replacement parts,but a very fiddly job to do because the bolts are difficult to access. By then I had already replaced almost all of the front suspension, so maybe I would start with these bushings first.

The workshop manual says that you have to drop the front subframe, but this is not necessary.
I found out that the best accessibility to the bolts of the brackets of the sway bar bushings is if you remove all of the cooling houses between radiator and engine block, but others have done it from the wheel well. If you search the forum , you should be able to find some threads about it.

Best regards,

Thomas

 

If one has to replace an earthing stud with a bolt, it is possible to buy titanium bolts. This metal is the most compatible with aluminium, as its use in aircraft shows. Yes, they cost more but would permanently fix the problem.
https://www.pro-bolt.com/titanium/

 

Good tips, thanks guys. Thomas, I believe I disconnected the front sway bar at the drop links when I replaced the front air shocks a few months ago. At the time I do not recall any slop in the heim joints of the end links, but I did not inspect the bushings as I left the bar in place. I think I need to order a pair. Thanks, Andy