Upgraded to GM HDD navigation radio but there's problems

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UplevelDave

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So I've done a lot of research online before the swap - I have a 2008 Tahoe LTZ that had factory navigation, and I installed a HDD nav radio from a 2012 Yukon in it using the adapter harness. The radio is properly configured to the truck, everything works great. Except...
For some reason, the radio will NOT turn on unless the engine is actually running. If you turn the key to accessory, nothing. Run.. nothing. Start the engine? Radio comes on. Turn the engine back off one key position? Radio is back off.

Let me start by saying it's not a wiring problem. This is a GMLAN or a radio problem. So the question is directed at someone who knows GMLAN a little more in-depth or has done this swap.

When I was first looking at doing the swap, a lot of websites that sell the whole setup say "Fits 2007-2014 Tahoe, Yukon etc" and then one or two places said "Fits 2009+, or doesn't work in 07-08 trucks" and one place I called... MVI maybe? The tech support guy said "No, there's electrical differences, the radio won't stay on in 07-08s" but couldn't elaborate. It made no sense to me because 07-14 Tahoes all use 29-bit GMLAN. And many others I spoke to said "That's nonsense, it works fine in 07-08 trucks" including the GM radios guy I bought my harness from and who did the radio programming.

All of that being said: I deal in auto salvage, I do know a fair amount about the GMT900 trucks, and there were subtle differences between 07-08 and 09+ trucks, parts did change like the power liftgate assembly and many electrical modules are 07-08 only. BUT: The body control module for this truck shows fitment from 2007-2011. So that alone tells you there aren't drastic differences.

The other issue I noticed is that the rear DVD screen no longer works. The backlighting and IR comes on so it's getting power, and the RSE/rear climate control on the back of the center console comes on and works just fine. But the screen will not show anything, I can only play movies up front.

It's strange how when you look into doing this swap, there's lots of forum success stories. There's instructional videos online, but: a) I can't find a single person who's done this on a 07-08 GMT900, it's always newer trucks. and b) Only ONE video makes a casual mention of "Oh, by the way, you have to cut this whole section out of the dashboard..." and then doesn't say why. There are more plugs and they are bigger, so the plastic at the rear of the radio "bucket" has to be cut out a bit. Not as drastic as the video shows but definitely needs to be done.
 

Doubeleive

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from what you are describing it sounds to me like either the harness is not quite right or the programming is not quite right. particularly if everything existing is known to be working before the swap., your rear dvd isn't going to suddenly stop working (very unlikely) same for rap power.
 

swathdiver

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Nice to have you here Dave. This radio stuff is all Greek to me. There are Nav radios for use with rear entertainment system (U42) and without, separate part numbers and RPO codes.

For example, the RPOs for a 2009 with Nav radios was U3U and UVB. The former without U42 and the latter for use with U42.

@iamdub
 
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UplevelDave

UplevelDave

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The harness is a premade professional conversion type of deal, so it wasn't anything cobbled together. There must be one company that makes them and probably 4-5 different "OEM radio" companies online all sell it. The reason it's not a wiring issue probably, is because putting everything else aside, these factory radios just need three wires to work: 12v constant power, ground, and GMLAN (data). There's no separate wires for accessory mode or run, etc. So as long as the radio does turn on, that means it's getting a signal from the BCM that says "Power up, the truck is on". I was mainly hoping someone on this forum also did this swap to their 07-08 truck.
 

fiatdale

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I was one of the first to do this years ago on my 07. The RSE didn’t work off the bat, I had to modify the harness because it was not correct (purchased from CPS Audio). I would challenge your wiring harness - I would bet tall the problems lie there.
 
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UplevelDave

UplevelDave

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So putting aside the RSE stuff, to clarify you have a 2007 truck and installed the 2012-2014 HDD radio, and it powers on/works fine with key in Run or Accessory mode??
 

kbuskill

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Just throwing this out there...

Does your keyless entry and interior lights function correctly?

The RAP for the radio keeps power going to the radio until a door opens then shuts it off. If you had a bad door switch the BCM would think a door is open and turn power off immediately. Of course you would probably have a message in the DIC about a door being open as well... just a thought.
 

fiatdale

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While I dont have it anymore, I DID have a 2007 Tahoe LTZ with RSE (no factory nav at that time) and added 2012 HDD Nav from CPS Audio - plug and play - yes. Everything powered on / off / functioned completely normal with the exception of RSE, and that was a wiring issue in the harness.
 
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UplevelDave

UplevelDave

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Yep, keyless entry and interior lights are fine, RAP works for windows, no other issues with the truck. Also the original navigation radio from 2008 works as it should when installed. This replacement was configured (at least supposed to be) specifically for this truck with its specific options.. it was originally from a Yukon Denali so it had to be changed to non-Lux, show a bowtie logo, configured for RSE, etc. I emailed Oem-Radios, who did the configuration, last week and haven't heard back.
 
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UplevelDave

UplevelDave

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While I dont have it anymore, I DID have a 2007 Tahoe LTZ with RSE (no factory nav at that time) and added 2012 HDD Nav from CPS Audio - plug and play - yes. Everything powered on / off / functioned completely normal with the exception of RSE, and that was a wiring issue in the harness.

Well that makes me happy to hear, my main concern was that there is some sort of BCM difference with 07-08 that cause issues with the newer navigation radio. I'll track this down one way or another. I think the next step is that I'm going to pull the radio back out, and just use a test harness with power/ground/GMLAN (and nothing else) and hook directly to the DLC under the dashboard and see how it behaves, bypassing the adapter harness and radio wiring.

I shouldn't have put the trim plate back on, ugh I dread taking that off again. Those clips are so tight it always feels like you're going to destroy your dashboard, snap off clips, break the bezel, etc. Even with a trim tool.
 

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