I did this DIY How-To years ago...back in 2004 actually and it’s been featured in the Audiworld.com Tech Articles ever since. The write up was for the B6 Audi A4 but most will apply to a lot of other model years as well.

Escort sells the Direct-Wire SmartCord for $34.00. The Passport 8500 X50 comes with a SmartCord, which has a built in mute button and warning LED, but it’s the cigarette lighter type. I started messing with the cigarette lighter power adapter and after taking it apart, realized I could make a Direct-Wire SmartCord similar to what Escort sales.

The pictures jump around a bit in the order that I worked on it. It took me a good couple of hours but it was very easy and fun work. This is going to be a picture by picture how to..but I've added some comments here and there to clarify.

Before:

After:

The charger is held together with two screws. Once these are removed, you can separate the two pieces and expose the inside. As you can see, the front display is a sticker/decal.

$6.99 12 ft. black telephone cable from Radio Shack with RJ11 plugs on each end.

Take a look at the plug ends. The one on the far left is the Passport's original RJ11 plug. The telephone cord has one end that matches (on the far right) and one that doesn't (in the middle). Cut off the end that doesn't match (middle) and keep the one that matches (this end will be plugged into the detector).

As can be seen in the picture, once the black outer sleeve is cut back, the four wires match the wires used in the Passport's SmartCord. Simply match them up.

To remove the map light/sunroof controls, start by popping off the first light cover by simply using a butter knife.

Do the same with the rear light cover. They are both held in by clips, no screws to remove.

Finally, remove the two screws shown and pull on the entire assembly, it will easily lower

down.

You will be able to see the windshield through the hole shown below. This is where the telephone wire will be fed through.

Push the cord out the other hole above (it will form a "U" going in one side and out the other) then pull it along and push it under the headliner, down along the A-pillar and along the dash.

Once you remove the fuse box cover (simply pops off), pull the wire that was fed along the dash.

Reach behind the dash and push out the cover where the display will be installed.

The display decal can be used as a template for drilling the necessary holes.

Use a piece of tape to hold the template in position. Start with a smaller drill bit and go larger as needed.

Half of the lighter plug will still need to be used to hold the circuit board in place.

The corners need to be shaved as well as the bottom slightly. For this, I used a large file.

Cut off the end of the plug.

On the circuit board, strip the wires as needed. For the 12v+ and the negative, solder extension wires that will reach from where the display will be located to the fuse box area.

Solder a connector on the black negative wire for the ground.

Use one of the screws that held together the cigarette lighter plug to hold the circuit board to the modified plug.

After feeding the telephone cord through the hole, splice the ends of the wires.

Solder the wires (color matched) and electric tape them.

I used the #5 fuse which is for the telephone/tire monitor/maintainance. It is a 10A fuse which I figured would be sufficient. The #5 fuse is a switched fuse which will only activate the detector while the car is on.

Wrap the 12v+ (red) wire around one of the prongs and place back into the fuse box.

Ground the black wire to the bolt shown.

Insert the circuit board/half-plug in the cover and install back into the dash. (The circuit board/half-plug will need to be glued in which I didn't do yet).

The green LED will be constantly lit during operation. The wires for the red and green LEDs can be swapped if you prefer the red LED to be on at all times and the green to flash. A red LED can also probably be purchased at Radio Shack to replace the green LED.

If you want to do the install without the SmartCord conversion, you can simply splice into the sunroof 12v wire and ground the detector on the screw hole pointed out (screw holds light/sunroof assembly)