Touch screen not allowing optical signal to cd player

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Varks74

Member
Posts
15
Hi all, been chasing a blank screen issue on my 2007 L322,
initially i had no power at all and no blinking power button light, I solved that with a new IHU, now i get the flashing light but nothing else,
I have tried 3 screens and get the same issue, if i use a MOST loop bypass plug on the optical input i get a signal light at the cd player, if i plug the lead in to the touch screen i don't get anything at the cd player
I am waiting on some needle probes for my my tester and i will see what i have at connector A (20 pin plug) see attached picture, i am also now going to check that the MOST signal is correctly orientated on connector F (in the other picture) as i have read that these get messed with by previous owners chasing faults,
has anyone seen this issue before or am i barking up the wrong tree entirely?
A lot of people have said its the bluetooth module but i'm not getting a signal that far in the system at the moment as i have disconnected the male/female connector in the rear compartment and unless i loop the screen i get no signal back there anyway, so the problem must lie with the screen surely?
i'm guessing the touch screen requires power to allow the optical signal to pass through it and onto the next module in the MOST system,
It'd driving me insane and until i get it sorted i'm reluctant to put it back together,
Please help #desperate
 

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Varks74 said:
A lot of people have said its the bluetooth module but i'm not getting a signal that far in the system at the moment as i have disconnected the male/female connector in the rear compartment and unless i loop the screen i get no signal back there anyway, so the problem must lie with the screen surely?
Click to expand...
What did you disconnect and did you put a loopback on the plug you disconnected?
 
backinblack, cheers for the info bud, yeah i used a loop for the connector that plugs into the touch screen, that enables me to get the red led at the connector for the cd player, if i don't use the loop and plug it into the touch screen as normal, i don't get a signal at the cd player, which leads me to think there is an issue with either a pin on the connector or an issue with the audio relay, i am going to try and make sure i have power at all of the relevant pins on the touch screen connector, as well as the ground pins, i need to find a wiring diagram for the audio relay and i can then check that too, i have swapped it out for another one to make sure it wasn't the relay,
 
Looking at the diagram you sent through, i may need to try something else, i don't think i looked at the connector in the back once i connected the screen as i was lead to believe that the CD player was next in line after the screen, so will look at that later today,
 
When you loop something out it just bypasses that unit so the light signal will still continue to the next one following the ring. You may need more than one loopback cable.
 
is there a specific order the loop goes in? I was working off the assumption that the IHU is where the signal originates, then it goes to the touch screen, after that i thought it went to the cd player, i do get a light at the cd player if i loop the connection to the screen, if i connect the screen i don't get a signal at the cd player which is why i thought the issue was with the screen,
I will check if i have a signal at the connection in the rear compartment with the screen plugged in although i can't see how it would change things,
As i don't get a signal at the cd player with the screen connected, I unplug the screen and plug in the loop to the lead that is supposed to connect to the screen and it allows a signal to the cd player, regardless of anything else plugged into the rear compartment,
 
It does sound like a screen issue. Have you got power to the screen?
There may be more than one power connection but I don't know.

Got some stuff to do so won't be around for a few hours.
 
I will check the power supply to the screen this evening and post up the results, thanks for your input buddy, much appreciated, just hope i find something wrong,
 
kds, i've not got an optical signal getting to the back at the moment, so struggling to see that anything in the rear would be causing the issue,
First job when i get the chance is to check the screen is getting the correct power at the correct pins, just means i need to take the dash out again, I am toying with the idea of using one of the spare screens i have and powering it up on the bench to see what i get on the screen, I know the previous owner fitted a replacement amp, so may have to strip everything out of the rear compartment and start again,
 
I did find this online, it was an AI answer to whether a faulty amp would still allow an optical signal to the rear modules, but it would explain my issue:
No, with a faulty amplifier (amp) in an L322 Range Rover, the optical signal may not reach the rear entertainment modules. The amp is part of the MOST system, and a faulty amp can disrupt the entire system, including the transmission of signals to the rear modules.
 
That's AI for you. It doesn't know the amp is already in the boot. You said there is no signal to the amp so if you put the loop bypass on the screen do you then get it at the amp?
 
backinblack said:
That's AI for you. It doesn't know the amp is already in the boot. You said there is no signal to the amp so if you put the loop bypass on the screen do you then get it at the amp?
Click to expand...
I've not tried that as i have no signal getting to the rear (disconnected the white wrapped optical harness from the female connector as it enters the rear compartment, no signal there if the touch screen is connected,
 
just re-read your reply, yes, if i loop the screen, then i get signal to the rear, i might just put the old Amp back in, as i wasn't sure if the amp is also hard wired to the screen, so if it's faulty maybe it's not allowing the optical signal to pass through the screen, the previous owner replaced the amp thinking it was the initial problem of no power to the screen, I found that it was a faulty IHU, so the chances are the original amp could be ok, maybe the replacement amp had an issue he didn't know about,
 
Does the screen show any of the other functions like suspension or settings or is it completely dead?

I had my screen go off once when I first got it but it came back after ignition off and on again.
 
backinblack said:
Does the screen show any of the other functions like suspension or settings or is it completely dead?

I had my screen go off once when I first got it but it came back after ignition off and on again.
Click to expand...
No bud, no signs of life on the screen at all, the only thing i now get, since replacing the IHU is the flashing orange light on the power button,
 
I will try and get some time later to double check the in and out optics to make sure they are in the right orientation, I've lost track of what i have done so far, i will put the bypass loop on the rear connector with the rest of the rear optical harness removed and see what i get and where in the front section, with the bypass loop fitted to the rear connection i should get a continuous signal from the IHU, through the screen and onto the cd player optical plug if the cd player is the last one in the loop as the diagram suggests,
maybe i didn't try that with the loop at the rear as i was expecting the cd player to be after the touch screen, if that's the case then maybe it should work,
I will try that and let you know, i just need to remember how the rear harness connected, so i have everything in the right order,
 
According to the diagram the amp to the screen is bi-directional so yes maybe the amp is not turning the screen on. If indeed it is supposed to but I have no idea on that one.
 
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