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Don 'Mo Lurch'
Don 'Mo Lurch', Cadillac Technician
Category: Cadillac
Satisfied Customers: 20660
Experience:  GM, Cadillac Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.
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I'm working on a 2007 Cadillac escalade and trying to access

Customer Question

Hello! I’m working on a 2007 Cadillac escalade and trying to access / send an aftermarket video signal to the oem rear LCD screen. First some background: I have already installed an aftermarket Bluetooth phone and lockpic. I can now view video directly
from my iphone which displays it to the in dash LCD screen in the dash of the car. To make everything work I also installed a hardwired power inverter and an apple TV Bluetooth/wifi device under the dash- so all is wireless and works as it should on the front
lcd screen. My last goal is to access the oem rear lcd monitor so that I can simultaneously view the video image on both the front and the back lcd screens. Because I can see the video image with audio on the front screen I have access to all necessary wiring
to move the image to the back monitor- power, ACC, audio leads, and video leads- all from the front dash. I have already accessed the rear lcd monitor wiring, and have identified both video inputs (positive and negative), the power wire (12v), and the ground
wire (there are actually 2 grounds). Although the rear lcd has a constant 12v power wire (BATT), it is not actually powered on at all times. The rear lcd monitor is only turned on via some type of signal from the front OEM headunit. This is where the trouble
starts. I do know that the rear lcd is turned on when either: 1. a DVD is inserted in the main in dash head unit (and identified as a DVD, not just a music CD) - or 2. it is turned on when AUX is chosen on the main head unit. On viewing the diagram (link below)
I thought that if I accessed the “Entertainment remote signal” (lead 8 ) I could just move an accessory wire to lead 8 - which I thought would signal the LCD to turn on (it already has constant power to lead 7) surprisingly I found that lead 8 WAS ALREADY
POWERED. Lead 8 appears to be turned on with the key in ACC or ON position – but even with lead 8 powered in this way, the rear monitor is still off and unpowered (despite having a constant power source BATT from lead 7) So again, the rear lcd monitor is being
turned on via some type of signal from the front OEM headunit, but at this point I don’t know how it is being signaled. Additionally, I have tested lead 8 when the rear lcd monitor is actually on (as cadillace OEM intended) and there is still power to it!
At this point I’m at a loss. Since then I have completely dismantled the LCD screen to attempt to bypass the remote lead and power the unit directly, but the wiring directly inserts into the circuit board of the LCD. I’m ready to just by a separate LCD screen
and replace the existing OEM screen if I can't make this work- unless you know a way to power the OEM rear LCD screen (ps I’m prepared to wire any separate circuit I need to to make this work – I don’t mind manually activating an after market single pole switch
or two if I need to) Thanks again for responding - any ideas are appreciated! Heres the LCD input detail link: https://www.dropbox.com/s/e1wfslljnlu2zgu/dvd-07-06.gif?dl=0
Submitted: 1 year ago.
Category: Cadillac
Expert:  Don 'Mo Lurch' replied 1 year ago.

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sorry for the delay............
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Greetings...... “Hi, I’m Don (aka MOLurch) and I look forward to helping you!”
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I can post GM Schematics showing Signal & Audio Input / Output, but I cannot tell you "how to connect", as I do not know what & how you have wired the system & cannot see it
IF you need the Schematics, please accept the "Offer for Additional Service that I have sent

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IF you need more information, please ask "prior" to Rating.
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The way it works is, "I supply the Answer....You Rate my Answer"
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Please take a moment to rate my service so that I can get credit for my time.
NOTE: Do NOT Rate on how much TIME you waited, because I am not on 24 / 7 and I answer as soon as I see the question.
The question will still remain open for follow up questions if needed.
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Customer: replied 1 year ago.
Thanks Don, I appreciate your response - in fact you helped me last time and all went well according to your info then!unfortunately I have seen all the schematics for the head unit, junctions, and rear lcd - so additional ones won't help here
that's why I detailed the response so wellI know and understand that you can't see my wiring, but respectfully ***** ***** know how to connect an lcd screen in an auto to get an image (I mentioned i have isolated and am aware of all connections needed to get video to the lcd screen) i just cannot isolate the mechanism for how the rear lcd screen itself turns "on".. again the screen itself has 12v constant batt power -I just can't figure out the mechanism that the main headunit communicates to the lcd screen to turn "on" when neededits not a simple ACC or BCM that triggers the lcd unit "on" (again outlined above) as the "entertainment remote enable signal" from pin 8 (circuit 7066) has constant power with the key in either the ACC or RUN position. Even with that constant power, the lcd screen is "off" and unactivated.When a DVD is played normally and the lcd screen is activated (through some type of headunit signal) or "on", pin 8 still has powerif the schematics can tell me the mechanism that the main headunit communicates to the lcd screen to turn "on" when needed they would be helpful, but having seen all the schematics for this system I don't think they will answer my question- thanks anyway for your response - I'll consider this thread closed unless you think there's an answer for me out there.thanks again anyway!
Expert:  Don 'Mo Lurch' replied 1 year ago.

If you have all schematics, the Front & Rear Screen gets its DATA to turn on from the BCM, as most GM Radios do.
Schematic will also show the Front "trigger" is tied to the Rear "trigger" which powers "both"
The BCM has to have a request from the Ignition, Radio On to send the DATA Signal to front & rear screens.

IF you would like to keep this open, I can OPT OUT & Relist to see if someone else has that info
You may also want to join "the 12 Volt" & post same in Video Forum
http://www.the12volt.com/installbay/vehicles.html

Customer: replied 1 year ago.
thanks again anyway Don - forgot to mention that already tried paralleling the front bcm trigger to a lead i connected to pin 8 on the rear - with no success. so please just go ahead and close the thread- you've got a lot of experience so I doubt its possible- thanks again!
Expert:  Don 'Mo Lurch' replied 1 year ago.

BCM should be a Ground - signal / DATA