My dash board on my RRS 2021 lit up like a charismas tree, engine management light, brakes were rock hard and hard to apply, when I did, with force they would stutter, push back on my foot, vibrating , like a nervous twitch.

I had these faults show on the display
Hill decent control not available
ok to drive with caution Stability control not available

I scanned it got these codes
U01B4-87
U3006-00 Control module input power A
U0046-81Vehicle communication bus C - invalid serial data received

I tried to charge my main battery up as it was dead, it wouldn't hold the charge, got prices from Jlr to replace and thought id change the Aux battery while I was at it

JLR Cost
Main battery £357.52
Aux battery £226.00
got the make from the part numbers, they are Exide 960 AGM main and Exide EK151 AGM Aux

Google search found Tanya battery's
Exide 960 £133,
AUX EK151 £43
Next day delivery £19

I put them in and the disco lights disappeared, brakes work as they should and all fault codes disappeared

Problem Solved.

Hope this helps someone in the future.

Even cheaper on ebay and no delivery charge Always listen to old people or when they die you will live on in ignorance.
The avatar is a picture of the man with a big cock.
Learned to 4x4 on 100 mile beach and Frazer Island QLD
Dont spend money on old cars you will never get it back

Did you do a BMS reset?

I changed the battery on my wife's car and my MOT garage told me it should also have the BMS reset which they did for me (they are supposed to charge for it but did it as a goodwill gesture).

I asked about the reasons for doing the reset and he said if you don't reset it, the new battery will be dead within a couple of years because the charging profile will be wrong. No idea if this is garage bs but as he did it foc suspect not? MY17 RRS 4.4d V8 Autobiography - Aintree Green (also referred to on Topix as British Racing Green)

Yep Bms reset is definitely recommended, i just replaced mine all together, it was cheaper than going to a workshop