I recently purchased a 2012 Ford F-150 Lariat for towing a travel trailer. It came with very nice large tow mirrors that had manual telescoping and folding. As is my usual behavior, I immediately decided I needed power folding mirrors for pulling the truck into the garage.
I found some aftermarket retrofit kits that add power folding mirrors for the 2012, like this one from Trail Ridge. The kits either assume the truck already has power folding, or adds the ability to the truck manually like this kit from Boost Auto for over $1000. I wanted to go with the cheaper Trail Ridge solution, but what wiring and programming would be required to make my truck think it has power folding?
From online searching it appeared my truck could easily support power folding since it already had power mirrors by adding a few wires between the mirrors and the mirror adjustment switch.
However when I went to add these wires to the mirror and switch harness they were already populated with wires! The actual folding control is done within the Driver Seat Module (DSM), and the functionality is enabled through software.
Searching for more information, I stumbled upon a PDF documenting how another F-150 owner was able to get a dealership to reprogram the DSM to turn on the power folding feature the truck was already wired for. I didn’t want to waste multiple weeks trying to coordinate this and pay for a dealership to modify my DSM, so I turned to Forscan.
After acquiring a free 2 month license, I used Forscan to modify the DSM programming to enable the power fold functionality. If you take this path be sure to create a backup of your programming in case you mess something up!
Under the Configuration and Programming tab, I modified
744-01-01 F840 85
to look like
744-01-01 FC40 89
I Clicked Write and the value was programed into the DSM.
Once I turned the ignition off and back on I could hear the sound of a relay clicking when I pressed down on the mirror adjustment knob, meaning the programming was successful!
After installing the mirrors and connecting the harnesses folding/unfolding works!
The new mirrors had running lights instead of the puddle lamps like the original tow mirrors had. The running lamps were connected to the puddle lamp wiring meaning they would only illuminate when the interior lights were turned on by opening the door, unlocking the car, etc. I rewired the harness connectors on the truck side, connecting the violet wire coming out of the connectors to the running light circuit coming out of the BCM. I made sure to swap the lamps inside the mirrors with LED equivalents to reduce the amount of power draw hoping to not overload the newly tapped circuit.
Now when the headlights are turned on the bottom marker light illuminates!
