Press start button just to put the ignition on and the dash is not lighting up. That said it flashes up for about half a second and then nothing. Car will start then when I stop it, it won't start again.
Any suggestion before I take it to the garage.
Thanks in advance.
Terry

Check Battery and charge it.
Get a OBD2 code scanner that will also reset faults. Then scan again and see what you have. 2018 SE SDV8 4.4 Byron Blue

Already scanned and any faults reset. Battery tested by Green Flag and battery ok.

I had this on my previous RR, the dash display had failed and required replacement - the LR Warranty covered it, but it was expensive at the time from what the MD said. 2021 L405 Vogue SE 4.4 V8 DIESEL ~ #17

I did look at taking out the warranty but quite expensive. Kicking myself now it maybe a costly mistake.
Whats annoying me is it starts but no dash, when I stop the engine and try to restart it won't.

I presume you have had the car for a while all working good then suddenly you get this fault? Or did you buy it like this?

I would still charge the battery, and try again to run a decent OBD2 scanner erase DTC then run again.
Because I would think any failure (module, wiring, earth etc) would record an error etc especially if it fails to start engine.

The HS bus and medium speed bus connect to the Instrument Cluster also there is a permanent fused supply to the IC, certainly if IC does not start up, these would report error on these busses.

These cars are hungry for battery power and lots of Gremlins occur with bad earth point's/loose wires (both front wheel wells etc). Worth checking these points first. It's not amazing how ground faults and weak batteries cause so many issues.

Also is your fob battery good? because from WS Manual--- When the stop/start switch is pressed, if the keyless vehicle module detects a valid smart key in the vehicle the CJB (central junction box) transmits a hardwired crank request to the ECM. poor fob battery could be preventing start (second time you mentioned).
Also a failing/loose wire on the start/stop, brake switch, transmission switch etc could also be a culprit, as these report back to the ECM.

When the ECM receives a crank request from the CJB , provided the transmission control switch is in P (park) or N (neutral) and the brake pedal is pressed, it energises the starter relay. The energised starter relay supplies battery power to the starter solenoid, which energises and causes the pinion gear to engage with the ring gear.
When the starter solenoid is energized it also closes high-current contacts for the
motor, which connects battery power from BJB 2 to the motor to turn the engine.

Good luck! 2018 SE SDV8 4.4 Byron Blue

Had the car about 4 months now with no problems until now.

The battery was fitted brand new before I purchased the car. I did call out green Flag and the battery was the first thing he tested and was good to go.

It’s odd how the dash fault happened, it was after torrential rain up in Scotland. Car started and drove as perfect. After say 10 mins, 30mph a warning came up on the dash but was to quick to see what it was and the dash just went blank. Car still drove normally but no dash and no infotainment screen.

Parked up and thought turn it off turn it on but car would not start. As I found out later if I let alone for 5 minutes after it had gone into it’s sleep mode kinda thing the car would start but still no dash. With engine running the dash would flash up as if it was trying to boot up but only for a second or 2 then go blank again.
Basic scan and reset with iCarsoft LR V 3.0 but no joy. Shame I didn’t record the faults but I remember a Bus failure.

It did come up with did not recognise key, odd that as I did put a new battery in.

So me stuck up in Scotland with a caravan and a car that would start but no dash/info screen. Decided to go for it, hitched up and set off. Phone on the dash using google maps as it shows the speed. Fully appreciated that no dash meant no fuel gauge/temp and so on. Full tank of fuel and after 200 miles I’m home.
Parked up and same symptoms. Went out after a couple of hours and now the dash/info screen are working. You couldn’t make this up if you tried.

Going to see if it’s still works in the morning and go from there.

One thing I have noticed and it’s in the back of my mind. The rear off side carpets are wet, was sat outside the caravan (it wasn’t raining) and water was dripping just in front of the back wheel. Have put this down to the pan roof leak pipe thing and will look at this tomorrow. Not sure if this is anything to do with the above but can discount water getting some where and shorting out something?

Just as a note I did pull the dash out to get the model number and it turns out it’s a dash out of a Jag Pace.

Thanks for the replies and keep em comming
Terry

Ah now we have the back ground
Do the basics first
Did you put in a duracell fob battery, lots of stories on here where average cheaper batteries did not work.
Do you have both keys? then change both batteries.

Check all fuses maybe as you say, all this rain caused a short and blew a fuse/fuse link etc.

Look at WSM in WIKI, find electrical distribution/instrument cluster and fuse 6B (40A) in the Junction box-Battery supplies Junction box central check this.

Check under the carpets that were wet as items like amplifier etc are kept under seats! 2018 SE SDV8 4.4 Byron Blue

If it has a sliding roof this could be the problem...

That looks like a great fix on the YT video.
I surprised that there has not been a factory recall to change the drain components on those cars with a opening sunroof

Update, found this and it looked ok. However poured some water and then it pored down on the inside pillar.
?feature=shared

Game on to drill out and replace the drain spigot, what a job getting to the underside of the spigot. Didn't take the whole headlining down just the rear off side bit so I could get my hand behind.
The pain was the rear light/air vent, who the heck invented that bit of kit.
Anyway just done and I have convinced myself water ingress was giving me a fault with the dash/canbus.
Need to dig a little deeper and investigate what modules got water and dry them out a bit before I have anymore problems with them.

This fell out from behind the linning, any ideas?

Click image to enlarge