How can you tell if the TCU battery needs to be replaced? I replaced it a few years ago and don't think there was any sign other than I tried everything to get my In Control app to work, so it was a process of elimination. Well it is not working again and in sleep mode. I would "think" the TCU battery would last longer than 3 years but maybe not. I see Amazon sells them much cheaper than the dealer so at least is a bonus. Dealer cost was about $80 for my year-2016.

 

I don't know if this is the only sign, but one sign is you will get the message, "SOS System Not Available".

 

If you have access to a scanner you can monitor the datalogger values of the TCU BUB, or you can remove it and measure it. A properly charged BUB is around 4.2V, the ones I remove that are dead are usually right down at zero. Has your car had a dead battery or the battery disconnected recently? Anything that causes the TCU to lose 12v runs it off the battery and kills it in fairly short order if it's not put back onto 12V and allowed to recharge. It's really only there for emergency use, it doesn't last that long. As above you should get the message for limited availability if the battery is failing.

 

Also, the Incontrol seems to be sunsetting the older cars, your '16 may not be fully supported anymore. Might be worth a call to Incontrol to verify before you throw any parts at your car unnecessarily.

 

I had just renewed the In Control app in December. It was functioning correctly just prior. And my last TCU battery I had replaced, I never did get any notice about the SOS not working. I just couldn't get the In Control app to work, so I replaced the TCU battery and it worked again.

 

I have a MY 2017 built in 2016, so with transitional components. I renewed my InControl Remote in August of 2025 and also proactively changed the battery. All worked fine until this past December, 2025 when the app no longer worked, the car went to sleep and nothing I did would wake the car up. I have an appt with dealer to run a scan on it, but reading your post, I'm wondering if your fix may work for me? Replacing the 'new' battery is just a minor job IMO if I can get it all to work again. Is your Remote and Protect app still working?

 

I have never had the SOS not available show for me and I have replaced the battery before. Since the battery is less than half on Amazon compared to the dealer, maybe I will just buy it and try. I did this when I bought the last TCU battery and everything started working again. I just would THINK the battery would last longer than the 3 or so years since I installed it. And the install is quick and easy.

 

When does the TCU battery get recharged? All the time off the 12V or only when the car is running? MIne seems to be a bit erratic if I don't use the car a lot, so wondered if the charging is dependent on the car running.

 

I also never had the SOS show up, but proactively I wanted to change the battery. When I took the original one out, it was date stamped 2015, so a 10 year old battery.. I ordered the replacement that is in the car (since last August, 2025) from Amazon. I would be interested in knowing which vendor you purchased from. The first one I bought had no date stamp on it, even though the Amazon sale site photo showed a date. I returned it. I bought a second one from a different vendor. That battery was also shown on the Amazon sale site as having a date code. When it came, that one did not have a date code either. I decided to go with it and put it in. Remote and the app all worked fine for the 4 months from August to December. No SOS message, app and remote just stopped. The replacement process isn't hard at all, so would be willing to try a different battery, if you could let me know which vendor you used.
And I do think it's a rechargeable battery, so the car would need to run to recharge it.

 

I will let you know what I end up buying but plan on Amazon providing they take the return if this does not fix my issue. The battery in the car now is the OEM replacement I picked up at Jaguar a few years ago but it was over $80 from what I recall and hate to spend that knowing that its non returnable at the dealership and $80 when I can get a knock off on Amazon for $30.

 

Let me just say I recently purchased a TCU battery from a vendor on E-bay for about $25.00. When I received it, it was nothing like the one advertised. Not even close. I sent pictures of the battery to the vendor and they just either ghosted me or came up with some stupid question asking me it it fit right. After about 2 weeks arguing and sending pictures back and forth I finally got my money back. ( and of course it was a Chinese dealer). I finally decided to get one from a dealer I could trust ( FCP Euro) and paid a lot more money for it. But it arrived in a couple of days, was the right battery, and was dated Nov 2025. At least I now feel confident that this battery should last me nine years like my original one. I am only changing it due to age.I have never gotten any SOS messages or anything else.

 

Not having much luck with "jaguar telematics battery" on FCPs site. Did you enter the jaguar part number? I'm seeing some of the replacement batteries are a single cell rather than the 'twin pack' I have. TIA

 

Valerie: Yours and mine Jags are pretty similar. The Jaguar Part number for ours is T4N2591. This comes up as a direct cross-reference fit to the Land Rover part: LR046049.
So you want to order the Land Rover Part Number

 

https://www.fcpeuro.com/products/lan...0aAhOwEALw_wcB

Will spend a bit more time on research.

 

Here's an Amazon link I bookmarked some time ago for the F-Pace (ICTP). I got it from the F-Pace forum where someone had used it.

Amazon's compatibility says it doesn't fit Jaguar, but the LR part numbers are listed in the description.

 

Has to be running, takes an hour or more to actually recharge one if it's run down, it's a slow process.

If any of you guys replace it, measure the voltage on the old one, just for fun. I'm curious what you find. I have a good used TCU BUB I think, would have to dig through my toolbox stash. We replaced lots of them though.

 

I think my old one was 4.1V when I took it out, the new one was 3.something before I installed it back in July 2024.

 

The factory original that I took out August of 2025 currently measures 3.79. It has been stored inside 60 + or - degrees F.

 

I ordered the replacement from FCP and it came today. Not only marked as a Jaguar part, but also was date stamped, 11/2025 Voltage was at 3.5 Saturday project is to take out the Amazon one that I put in last August 2025, and see if anything changes. WML

 

Please post the outcome and great timing as I was about to buy one off Amazon for $38. I love FCP and nice bonus it is lifetime replacement. With the damn UPS costs, it makes returning the oil not a great deal but some savings is better than none. Need to figure out how to use the flat rate UPS option. But again, please let us know as I am itching to do this ASAP to see if it gets my InControl back running. Hate paying for something I cannot use.