Hello everyone.

I'm facing an issue with my 2014 Jaguar XJL 3.0l Petrol where the F28 fuse in the engine fuse box keeps blowing. The first time it happened, I was driving on the highway at speed when I noticed errors related to the transmission, suspension, and parking brake. I pulled over, but the car wouldn't restart because the fuse connects to the ECU, leaving the gear selector stuck in position. After towing the car to a garage, several blown fuses were found, including those for the ECU, horn, and another I can't recall. A scan showed U101 and U103 errors.

After replacing the fuses, the car started a few times, and I managed to drive home with a pack of spare fuses. However, the next morning, the F28 fuse was already blown before I even got in the car. I replaced it and went about my day, but after a short drive, the car wouldn’t start again due to the same blown fuse. I managed to replace it and get home, but the next day, the fuse was blown again. Now, whenever I try to replace it, it sparks and blows immediately.

From what I understand, F28 is linked to the ECU. I tried disconnecting the ECU and then inserting the fuse, but when reconnecting the battery terminal with the ECU unplugged, the fuse blew immediately. I suspect it might be a grounding issue or a wiring problem, but I also noticed that the manual mentions a VVT diode connected to this fuse, though I can't locate it.

Another detail worth mentioning is that the transmission was recently repaired due to a recurring problem with the heater core, where transmission fluid was mixing with antifreeze. The transmission was partially disassembled during this repair, and although I drove about 300km afterward without any issues, I’m wondering if something might have been disturbed during the repair.

I'd appreciate any insights or advice on where the problem might lie or how I could further isolate it.

Thanks in advance for your help!

 

Don't know but you have a short and need to trace it down?
Do you have a shop if you can't DIY this?
Again we need more information and getting the car scanned with SDD will be a big help.

Can you tell us what those codes mean? U codes are network codes and are very commonly related to low voltage and battery problems. Transient things that may or may not come back. So have they been cleared and checked again? Do they come back?

The heater core has nothing to do with the transmission. I think you mean the transmission cooler as that does connect to the cooling system?
The cooler is separate from the transmission and can be replaced on it's own without touching the transmission. Now you do bring up another point? Did the shop fill the transmission correctly and did they use the correct fluid?
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I'd like to try and resolve this issue myself since the car is parked at home in a covered parking spot on the second floor in my apartment complex. Getting a tow truck would be a hassle because I’d need to find a couple of people to help push the car out onto the road. But if I can't fix it myself, I'll have to figure something out.

Regarding the error codes: U0103-00 "Lost communication with Gear Shift Module" and U0103 "Lost communication with Transmission Control Module" both came up again after the fuse blew.

Additionally, I had a couple of error codes related to the knock sensor and the exhaust sensor before this, but I don’t think those are related to the current issue.

Yes, you're right, they replaced the transmission cooler, as well as the fluid and filter in the transmission because a significant amount of coolant had mixed with the transmission fluid. The transmission was flushed, and I believe they used the original ZF fluid. The same problem with the transmission cooler occurred the last time, and after repairs at the same garage, I had no issues for almost a year.

At the moment, I'm studying the electrical diagrams to understand what I can disconnect to prevent fuse from blowing and what I can check with a multimeter to narrow down the search area.

 

Thanks for the code identification. Since you have an XJ and NOT an XF what's below may not apply?

There is a known problem with the shifter assembly and your symptoms do point to the shifter assembly in the center console. The problem is usually this shows up on early XF's like 2009 and 2010? So not sure that is your problem?

Here is a detailed thread showing how to repair the shifter assembly and it also contains a TSB from Jaguar on the problem.
See if it might help?
XF Transmission Selector Module Problems-Failures

Since your getting the additional 2 digit code at then end of the main code I think your scanning with an SDD?
Have you gone thru the steps in SDD and followed what the recommendations tab or the extras tab has listed?
Might need some reprogramming or resetting of a module or two?
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I think it's a different issue because these codes are the result of the fuse blowing on the ECU, which causes the loss of communication with the gear selector.

Today, I had a bit of time and managed to determine that there is a short to ground on fuse F28. According to the manual, this fuse is also connected to the VVT diode, which I suspect refers to the solenoids. Could there be a short in one of the solenoids?
Think to try to unplug all the solenoids and check the short again, if it possible.

And when I disconnected the connector near the fuse box, the short disappeared. Maybe this provides some clue.