Smart Junction Box

[nautoncall]

So I was just reading the recent battery thread and this goes back several months to my “electrical gremlins” post. It’s not my battery!! I’ve driven hundreds of miles since replacement and STILL... my radio sometimes comes on at startup and sometimes it doesn’t. It will eventually come on at its on timeframe. When it’s not on, the door ajar light will not come on as well. Also my blinkers work occasionally and then will go off and then 15 or 20 minutes later they will work again. I’m almost certain it is my smart junction box. I have another car and I wanted to remove that smart junction box which worked perfectly and put it in the other car just to test. I’m asking how to unhook everything because there’s one small connection at the top with some kind of lever that I do not know how to unhook.

 

[Johntpr]

I've been down this road. Not a fun job. If I recall correct, just move lever up to release. I seem to remember some connectors located behind box also. Be careful you don't accidentally press the fuel cut off inertia switch in that area too, and be aware your key remotes are tied to that particular smart junction box. A new smart junction box comes with two new remotes. So don't lock yourself out. And disconnect battery for the job. I can scan and send a copy of that shop manual page if it helps.

 

[nautoncall]

Please do!! So sounds like yours went bad??

 

[B.M.F.]

The radio is power by the silver box rectangle box right by the smart box. Should say power supply on it.

 

[Johntpr]

 

[Johntpr]

Yes mine went bad......had an issue where my left tail light would stay on after car was turned off.

 

[w.a.nelson]

Yipes! Wouldn't wish that on anyone.

All Forum members cross your fingers when you read this. Perhaps this will drive away the wicked SJB spirits.

 

[Vincent998]

What does a new SJB cost (ex factory) and are they available?

 

[texas mongrel]

Sounds like your car was fitted with the special McLaren electronics package!

 

[nautoncall]

What does a new SJB cost (ex factory) and are they available?

I'll have to look up what I got quoted from Scott a few months ago when I was suspecting SJB failure and if I remember correctly an outrageous 1500-1700. That's why I want to try one before I bite the bullet. The radio thing I can live with, but the windshield wipers and blinkers I can't.

 

[Johntpr]

The part number is 5G7Z-15604-AD

 

[RPM217]

Sounds like that could be my problem too!! I have a new battery, and when I start the car, sometimes the radio, and signals, don't work, and anywhere from 5 to 15 minutes later, my blinkers start to work. I haven't taken the car down yet this spring...........but I'm guessing I'll have to bite the bullet, and get this taken care of!!!

 

[nautoncall]

Sounds like that could be my problem too!! I have a new battery, and when I start the car, sometimes the radio, and signals, don't work, and anywhere from 5 to 15 minutes later, my blinkers start to work. I haven't taken the car down yet this spring...........but I'm guessing I'll have to bite the bullet, and get this taken care of!!!

That’s EXACTLY what my car does!!!

 

[centerpunch]

My (non-FGT) experience with electrical problems like this (where there is erratic behavior of multiple components) is that the problem is always related to a loose or corroded ground connection somewhere in the car.

 

[Mpinelli24]

I had similar issues and found it to be the grounds. I cleaned all of the grounds throughout the car and the gremlins went away. No parts replaced.

 

[nautoncall]

Unless there is another ground besides the one under the hood off the battery, then my ground is good. What other ground is there?

 

[GT@50]

There are grounds all over the car. What's the most difficult thing to remove on these cars? The ground you need to clean is probably under it.

 

[nautoncall]

What does that mean? Take off every body panel?

 

[centerpunch]

The Wiring Diagrams manual for the car details all the grounds in section 10, then you can find the locations of each using section 151.

Not suggesting it would be easy, but it is possible.

 

[RPM217]

Update, my car is at Stamford Ford, getting all the fluids changed out, and addressing the windows, turn signals, etc. not working on startup, but having to wait 5-10 minutes (sometimes longer) for them to be functional. It is the smart module, and hopefully will arrive by Thursday, and maybe get the car back for the weekend. They do have a very competent GT mechanic there (Alex). I have just over 15,000 miles on the car, of which I've put on 12,000 of them.