Smart Junction box - Ford Mustang Forum
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post #1 of 3 (permalink) Old 12-04-2019 Thread Starter
earldavis1's Avatar
Joined: Sep 2019
Location: Los Lunas
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Smart Junction box

I experienced the fantastic water leak into the smart junction box. Everything when ging wow. One thing or another would stop working. I removed the junction box opened it up and cleaned and dried everything. I put it back in and everything seemed to work. After a couple of weeks, different things would quit working and then maybe start to work again. If I would disconnect and reconnect the wires from the SJB everything would work again. I thought it must be a connection. Then I was traveling through Utah at night in a snowstorm and every light on the car went out. I tried the disconnect re-connect and the lights would flash and go back out. Nothing was wet.
I ordered a new (not an Ebay used unit) and put it in. I reprogramed the key fobs and everything seemed to work.
Now to get to my point, In the morning or when the car has set and it is cold. I start the car and the fuel gauge or the speedometer either don't read or read wrong. I can go a little way and shut the engine off and restart it and everything works.
Do I need to have the dealer flash something and why does this only happen when it is cold

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post #2 of 3 (permalink) Old 12-05-2019
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Joined: Jan 2015
Location: North Carolina
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Hate you are having this issue, but it is very common unfortunately. I don't have a lot of experience as I haven't had the issue myself being I garage keep them and clean them out yearly to prevent it, but I know many members have. Have you done any searching on the forum as I know lots of threads and info on it. Either way hopefully a member that has had this problem will chime in soon.

Also looks like you relatively are new here. Welcome to AFM!

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(I have owned a few non Mustang cars over the years as well, but always try to have a Mustang with it or come quickly back to a Mustang!)
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post #3 of 3 (permalink) Old 12-06-2019
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Joined: Oct 2013
Location: whiting
Posts: 56
What did you do to stop the water intrusion? If you did nothing it will be back. The sjb will start the car, it's the option content that has to be programmed.
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