Please help me with my trailer wiring.

I have a 2005 Chevy 2500 Express cargo van. I recently bought a used tandem axle trailer that has a 4 wire to run the lighting and a 5th wire for the electric brakes. The van has a 4 wire plug hangin down next to the hitch, there is also a blue wire (which I am assuming is for the trailer brakes) and there is also a black/white striped wire (I have no clue what this wire is for). I had someone push on the brake while I put a meter on the blue wire and I did not have anything??? Does the vehicle have to be in gear or is there another connection somewhere that I should check etc? Also, I bought a 5 wire flat plug at walmart and I am assuming that I should be able to just hook up the 4 wires as they are and the 5th wire will go to the blue wire hanging down next to the plug? Or should I take this back and buy a 6 wire plug or 7 wire plug? And the same on the trailer? I have a tow/haul button on the dash, so I am assuming that this has a tow package and that the wiring should all be activated for trailering......I am an electrician by trade, but not much of an automotive electrician. Either way, I feel that I am capable of doing things myself as long as I can find someone to give me a little guidance. Your responses are very much appreciated.

Dark Blue is auxilliary power- must be connected up front in underhood fuse block- or a wired in brake controller- depending on how you intend to use it

Do you have your brake controller connected under the dash yet?

Also shown for that vehicle are the following:

Light Blue is stop lamp voltage

Light green is back-up lamps voltage

Red/white and Red/black are 12v battery supply

Brown is park lamp supply

Dk-green is right rear turn signal/brake lamp

Yellow is left rear turn signal/brake lamp

Black and white are both shown as grounds

Oh no. I thought that since it has a towing package, that the brake controller was the white plastic piece on the back of the brake pedal? Sounds like this is going to suck. I have 6 wires in the back, I have the 4 figured out for the ground, signals, etc. I thought that the blue wire was for the trailer brake hookup and all I had to do is hook that wire through to the trailer brake wire and it would work. There is also a black wire with a white stripe or white wire with black stripes depending on how you want to look at it. What is that wire for? Can you give me a step by step on what I need to buy and also what is needed to be done to make everything work on the trailer. I was thinking of installing some kind of all in one type plug so that it is easy if I need to hook up a different trailer with only 4 wires, etc. Thanks for you help. If it is easier, I can give you my email address to correspond?

You need to buy an electric brake controller. These come with detailed instructions on installation and operation.

Check out this site:
http://www.brakecontroller.com/?gclid=CLXko_2M7pYCFQE0xgodYmq4-w

I have used several of the "Voyager" model that is shown on the site, with good results.

Generally light trucks do not come with electric brake controllers from the factory, even if the 'trailer package' is ordered. Such controllers are usually added by the dealer if the truck buyer needs one. They are obvious as they sit at the bottom of the dashboard within easy reach of the driver.

Please note that proper electric brakes are not like an on/off switch. The controller, when properly installed will sense the rate of decelleration that the truck has and apply the trailer brakes accordingly so the trailer will slow down in a similar fashion.

Also, note the controller has a manual brake lever so you can apply the trailer brakes without stepping on the truck brakes. This is a vital safety feature because it is useful if the trailer starts to get out of control, like wobbling back and forth etc.

The brake controller must be installed according to the enclosed instructions. Usually it must be installed at a certain position to operate properly.
As for wiring, they usually have a positive wire switched to the ignition, a positive wire switched to the brake pedal and one wire going to the trailer brakes. It's an easy installation.

BTW pop the wheels off the trailer and inspect the brakes. Often trailer brakes are not maintained properly. You may find you have to re-do the trailer brakes so they work safely.