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Old 11-07-2006, 09:41 AM   #1
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7 pin trailer wiring harness kit

Can someone tell me why after I installn the 7 pin trailer wiring harness, that I have to have the dealer hook up the scanner and flash the computer. The install is pretty straight forward, you tie into the left taillight with pig tails off the harness, run wires up the frame that hook to the battery (I assume for a charging wire at the rear) and run a blue wire in the cab (I assume for a brake control if you installed one)??????? Seems odd to me!
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Old 11-09-2006, 05:39 AM   #2
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The only reason that I can think of, is that the computer is interlaced with the entire electrical system and adding extra components would interfere with its decision making. I think I remember having to do that to some of the corvettes I worked on. Similarly speaking the computers on the vets are so interconnect with the structure and components that if you added anything to them them they shut down, to the point of me having money taken out of every check for almost a year to pay for a 10k dollar dash and a computer on one of those vets for zapping it and making it smoke quite nicely (I was working on the tail lights adding an after market lighting system). With the JK being so new its kinda hard to say though.

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Old 11-15-2006, 08:34 PM   #3
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Unless you're tapping into sensors or busses with that 7 pin trailer harness (which you're not) - no you shouldn't have to reflash the PCM. Who told you that?

It could be a dealer liability thing where they want to flash the PCM with some sort of "tow package" specialized program (maybe doing something with your brakes, or shifting, I dunno). I doubt it's realistically necessary - so if it costs you a lot of money I'd just skip it. The blue wire is for an electric brake controller - but I doubt it's a good idea to tow trailers big enough to utilize electric brakes in a TJ.

If you don't plan on needing electric brakes (in case Jeep has a brake controller built into the PCM - which is weird since Wranglers don't make for good towing platforms) - you shouldn't reflash.
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Old 11-15-2006, 08:55 PM   #4
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Most of your newer trucks have pre wired harnesses........you should not have to Jerry rig this at all. All I did to my 02 Chevy, was tie into the pre- existing wiring, with the brake controller, and presto, I was done.
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Old 11-16-2006, 10:30 AM   #5
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I here what you guys are saying and it seems weird to me, I have wired many trailer plugs, but I have been told by my Jeep dealer and all the other places I have found the OEM wiring kit, ehttp://www.justforjeeps.com/trtowwihakit1.htmlven

Might be a towing tune download...that would be cool!
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Old 11-23-2006, 07:52 PM   #6
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Hey, Blade, that doesn't make sense to me either unless things have changed so much since I purchased my '04 Unlimited. I purchased the Mopar harness and did the install myself without any problems just as you did and the computer read the "new hardware" on its own without any outside intervention. There was no need to scan anything then and that's 3 years ago! By the way, the blue wire is for the electric brake control which I have because I pull a 3,000 pound travel trailer as well as take it offroad. Are they simply using this as an excuse 1) to check to make sure you did it correctly and/or 2) to get the bucks they didn't get because you did the work? Either way it seems very odd to me. If it's working, drive it. Hope this helps.
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Old 12-15-2006, 12:31 PM   #7
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There is no need for a compluter flash for this or the cruise control, it is just a dealer ploy to get in your pocket for $50-$75 for a reflash and all they do is log in your changes to their data base.
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Old 09-04-2010, 11:51 AM   #8
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hmenker or blade, I have just purchased a popup to pull with my 08 JKU. I wired a 7 pin to the existing 4 pin on my bumper so I would have lights coming home with it, but I would like to use the brakes as it is near towing capacity. For this reason I am thinking of getting the 7 pin harness. I say all this to ask this, do I need to purchase a seperate brake controller to mount in the cab or is this a feature built into these vehicles once you install the harness? Hmenker, I noticed you pull a travel trailer and use the brakes so I thought you might know how to do this. Thank you guys for your attention.
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Old 09-06-2010, 02:53 PM   #9

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I had a brake controller installed by my local travel trailer retailer. It was a piece of cake. I handed them the keys, waited in their waiting room, they drained my wallet of some dollars too insignificant to remember as it was done two years ago they installed a controller and a round trailer plug on the back the same as the electric brake trailer that I was intending on pulling. They said it was the standard plug for this purpose. All works well. When I pull other trailers I just plug in a four wire adapter into the round plug they installed and I'm on my way. The adapter makes it so that you don't have to have two plugs on the back, just the one.

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Old 11-17-2010, 09:45 PM   #10
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Lots of stuff on towing. I'm planning on adding a class three hitch and a 7 wire harness to a 2011 unlimited I'm picking up Friday (first Jeep) Question I have is in the Jeep brochure the factory Trailer Tow Group includes above 2 items and a "Trailer Sway Control" is anyone familiar with this item. Is it the shock like arm that goes between the Draw Bar and Trailer or something else? Heavier permanent sway bar? Appreciate your experience. Also, am I missing anything here. Thanks Frank
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Old 11-17-2010, 09:50 PM   #11
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By the way, am I posting this question in the right place? This thread seemed close to my own situation 7 wire and all. Just hope I'm not stepping, or driving, over anyone's toes here. Thank you all...FG
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Old 11-18-2010, 06:25 AM   #12
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TSC is an electronic feature to reduce trailer sway.


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