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Discussion Starter · #1 ·
My 08 F350 has 3 issues related to electrical. The power mirrors, dome light (map lights do work) and cargo light doesn't work. The lights don't work with the switch or the doors. I have good grounds and I jumped the mirrors to verify the switch works and it does. Checked all fuses and have power to fuses. I was told it may be the BCM body control module. Any other ideas??
 

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Does your Vanity mirror lights and engine compartment lights work? Which movements of the mirrors don't work?
 

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Discussion Starter · #3 ·
Does your Vanity mirror lights and engine compartment lights work? Which movements of the mirrors don't work?
Mirrors work in all directions with a jumper. Under hood light works and it does not have vanity mirrors as it's an XL.
 

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So the mirror it self moves and the whole mirror moves in/out (extends) and folds? I don't know what switch you're jumping?

I assume the red brake lights on the cargo fixture work but not the white light.

The SJB controls those lights on the 2008's but do not control the mirrors, BCM's are on the newer trucks
 

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Discussion Starter · #5 ·
So the mirror it self moves and the whole mirror moves in/out (extends) and folds? I don't know what switch you're jumping?

I assume the red brake lights on the cargo fixture work but not the white light.

The SJB controls those lights on the 2008's but do not control the mirrors, BCM's are on the newer trucks
My truck does not have power folding mirrors, just the glass is power and they are heated and have the turn light. All of which doesn't work. I used a jumper from the power lock connector to provide power to the mirror switch to test it.

3rd brake light works but no cargo light.

What is the SJB and where is it located?

Thanks
 

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Your Truck has a Smart Junction Box (SJB) that is like the Body Control Module (BCM) on the newer trucks. They are both located in the same location. Behind the passenger's kick panel.

In the old days the switch sent power directly to the motor, in newer vehicles the switch sends a low voltage signal to the computer (Inputs) and the computer sends (Outputs) 12 volts to the motor or lights. In your case the switch still sends 12 volts to the mirror but the computer sends 12 volts to the lights. The Computer (Module) can disable outputs that might have an overcurrent event to protect it and sometimes it can be reset and sometimes it can't which means a new module (computer).

This is why it is not a good Idea to jumper things, you could short out a $1200 computer.

I'm assuming that you applied power to the green with red stripe on the mirror switch?

That is why i'm asking all the questions. I hate being a parts changer. I have the wiring diagrams and if the light under the hood in the engine compartment works then two map lights should light up and the dome light might not. they both use the same ground so is it a ground problem to a power (hot wire) problem???

I had an 08 and now I have a 2013 that has a BCM.
 

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I'm assuming that you didn't check the fuses in the SJB for the mirrors which is F12. Or F21 for the turn signals in the mirrors
The moving of the mirrors is separate from the lights so that is interesting?
 

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Discussion Starter · #8 ·
Still a mystery...looks like a trip to the dealer is in order. Probably need to have it scanned to see if there are any codes showing up.
 
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