Hi all,
I am having a few issues that I am trying to trace down and I could do with a little help from those who have probably had similar issues if anyone could lend me 5 mins of their time?
Briefly these issues are;
Heated rear screen will not switch on
Both front and rear fog lights will not switch on
Front headlamp power wash will not work

When I first started looking into this problem it became apparent that the sunroofs etc. were leaking a bit and the footwell carpets were damp underneath - I put a de-humidifier inside over a weekend and the problem circuits worked but soon failed again. This led me to believe that damp might be an issue.

I had the BCU and IDM out and there was some evidence of corrosion on some of the tracks. All dried out, cleaned off and then re-coated with conformable coating.

I have had the BCU tested by Richard at Callrova (excellent service and really really helpful on the phone and email!) and it all appears to work and test out OK.
IDM replaced from another car that appeared to work OK (it was from eBay and the chap who sold it to me said it was OK but it is secondhand and not actually verified as 100% but I have no reason to doubt at this time).

From speaking with Richard, reading several other threads on similar problems and my own first thoughts it looks like I need to verify that the earths are all good. From looking at the circuit diagrams one of the earth points keeps popping up that needs looking at - C0551 that apparently is to be found beneath the footwell carpet. I have just taken the carpet out (quite damp too) but the earth point is nowhere to be seen. Does anyone have a picture/location where it might be? Am I being daft by looking under the wrong side? My Disco is a RHD - is this earth point/header actually under the passenger side carpet does anyone know?

Many thanks to anyone who has read this far and can spare a little more time to point me in the right direction!

Cheers,
Matt

You might want to read this. https://www.landyzone.co.uk/land-rover/electrical-issues.328782/page-2
and look at this https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwiv6Onok4zkAhUHKuwKHe38ChIQjRx6BAgBEAQ&url=https://www.pinterest.com/pin/11892386499879862/&psig=AOvVaw0o3B1VglghggdxdGegz4Fj&ust=1566208592789452
I don't know but I think I have heard that the earth point you are looking for is higher up than you might have looked and hidden behind something, a fuse box maybe?

Try this too, https://discoii.files.wordpress.com/2012/02/discovery-ii-electrical-library.pdf
All the way down in section 5 you'll find pictures of all connector points , it IS on the firewall. Between Brake pedal and footrest, if the picture is anything to go by.

It should be there on the RH side as in the pic closer to the console

Sierra, you are so good at downloading then uploading pics. I had the identical pic in front of me but just couldn't seem to do it! sure the op will find it helpful.

Many thanks guys, and yes, it did find it very helpful. Header now located and appears to be in good condition - now working my way through the circuits to see if there is any untoward resistance to the earth blades on the BCU and IDM plugs.

Cheers,
Matt

Well I have worked my way through pretty well all the circuits and I still have the same faults.
If it is not raining over the next few nights I will false feed the earth paths to see if it looks like the internal solid state switches have failed in the BCU & IDM.
I will also put a scope on the serial link to see if it looks like the comms change when buttons are pressed. Does anyone know if it is a CAN or RS232 or similar between the BCU and IDM?
Other than that I recon I need to talk with Richard again at Callrova.
Cheers all
Matt

There is a one wire serial bus between IDM and BCU

I guess it must be healthy as the immobiliser is functional, the mileage is not flashing nor is there the crossed B in the display but it would be good to see the waveform change when a command is active (or not I suppose to further aid diagnosis).