According to these two projects all the components would be stuffed inside the original radio chassis, so the look would be quite close to the original navigation system, and the whole system would be controlled by me through a touch screen. However, the small room behind the screen determines the kind of components you can use to build the computer.
Most of the parts were purchased via internet (eBay is your friend) and for people in the USA is even easier to get the components at a very good price.
Mother Board I decide to use an Epia M10000, that is 17x17 cm and very capable at a reasonable price.
Power Supply Very important decision. The M2-ATX is an intelligent PSU specifically recommended for in car solutions. It can control the way you want to turn on/off the system, avoid battery wasting, etc ..
The rest of components depend on what you want to get from the computer. I mean, I used 1 Gb RAM, an 80 Gb HD (from a portable PC), a CD/DVD RW combo, a 7” touch screen (Lilliput 629GL actually uses a HITACHI screen), USB 2.0 hubs to connect Bluetooth & WiFi adaptors, GPS antenna, memory cards, TV, etc
In addition, since I didn’t want to damage the original radio, I purchased another one so I could perform all the jobs before swapping the units. This has a collateral damage to your wallet because when you try to install another radio the systems is blocked (THEFTLOCK message at the DIC panel) so you must take the car to a Cadillac dealer that will charge you what they wanted to. They charged me € 80 for a 5 minutes operation.
Anyone with a Tech2 tool to be connected to the OBDII port below the steering wheel can do it, so there is no need to go to Cadillac if you have a friend with such a $ 3,000 tool ….
To me, the whole thing caused me a € 1,600.00 pain, € 1,150 for components plus shipping costs and the balance to pay some guys to integrate the screen and to build a custom harness to make possible to get the audio through the original speakers and keeping the factory radio, chimes and DIC information.
There is an useful web site to solve a lot of issues with GM vehicles until 2005, including drawings, diagrams, manuals, etc … but who knows how long it will remain open to us?
The first thing to get the radio out from the car is to pull the air vents and the climate control apart. You can do it with your own hands but it’ll be better if you use some kind of flat trowel. The radio is only fitted to the chassis with 4 bolts and after unscrewing them you must disconnect the ISO connectors plugged at the back side of the unit. Depending on which system you had the connectors panel may change.
The front face is a plastic piece fitted by 4 torx screws and 2 red connectors that interface with the main board inside the radio chassis. Once you disconnect them, you will see 3 different PCBs, one bigger for the DIC panel and 2 side boards for the control knobs. They are fitted with torx screws to a plastic mount as well. When all the parts are pulled apart, you can realize the actual size of the plastic you can cut off to room the screen bezel. Though I wanted to keep the original function keys, the guys I paid to do the job misunderstood me so they cut them off too so I had to change my plans a little. Finally I kept the buttons at the screen bezel so I could change the video source to get the images from the rear camera or turn it off manually.
This is a guide to integrate the screen, but be advised that the chassis from the factory radio is big enough to size it is easier to locate the boards inside.
Since I couldn’t get a spare radio in the same colour mine was so I had to perform some extra jobs like sanding and painting, so if you intend to do it the way I did do not make the same mistake. It looks great at the end, but it makes you waste a whole week.
The chassis is a 6 walls box that can be easily taken to pieces. The front wall is again fitted by torx screws but the upper and bottom walls are fitted by pressure flanges. Inside the chassis we have the CD player and the radio main board and both must be fully disassembled to have room enough to locate the computer components.
It’s all about screws so I will not explain the process. However the radio antenna is soldered to the chassis so we must unsolder it. If you are not going to use the original radio later you don’t have to solder it again, but I did it because I wanted to.
Since the Epia board is too big for the chassis, we must locate it vertically and that affects the rest of the components. I did it this way:
Hard disk and M2 power supply screwed to the back wall.
Mother board screwed to the side walls and the I/O panel headed to the bottom.
Radio main board screwed to the front wall, inside the chassis. The connector panel is headed to the bottom too.
Be careful to keep the holes clear in order to allow the cables pass through and avoid any kind of contact with the chassis, so use plastic bushings or any other means when screwing the components. The bushings will be useful to cushion the vibrations as well.
The touch screen is connected to the Epia via USB (to act as a mouse and keyboard) and the VGA port. You can get the power from any switched source (I wouldn’t recommend to use the climate) but we used the fuse panel located under the back seats. Since I will not use the audio, I cut the speaker and the RCAs off.
The video in connector is used for the rear camera, so you will be able to switch from the PC to the camera with the front PC/AV button of the screen. I used a 120º angle waterproof camera, it’s good and cheap but huge (3.5 cm diameter) so you can look for a minuscule but expensive Alpine model that works even inside a glass full of water if you can afford it (€ 300).
I recommend you to use one of the back USB connectors to plug the GPS antenna because I found some problems to configure it when I plugged it through the HUB at the glove box. I wanted to locate the antenna inside the central air vents, but it wasn’t able to get signal through the plastic (at least mine), so it’s now over the dash board.
I headed the USB cable for the HUB behind the glove box and I practised some holes to pass the cables for the CD/DVD combo, so everything is hidden from outside. Inside the glove box we have the combo, Bluetooth, WiFi, TV USB, Memory Card reader and some available ports to plug any other device.
The main point of this project is to build a custom harness so we could get the audio from the PC to the factory speakers and keep the radio as well. You will find useful these links to wiring a connectors diagrams for the CTS:
There are a couple of ways to get audio 5.1 from an Epia MOBO, it doesn’t make any sense if you are going to keep the factory amplifier because it only has 2 analog channels.
The idea is to use 2 parallel relays so you can switch from a source to the other by a button at the central console. Since the signal from the PC is too low, you must use a 2 channels amplifier between the computer and the harness.