Six easy ways to reach your pass thru wires for up fitters and profit

nullop

Tremor Member
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California
Current Ride
2021 F250 Lariat Diesel Tremor
I thought I'd share after a challenging day of getting my ham radio mounted.

Regarding the ham radio, I used a stake pocket mount from Breed Love mounts in the far rear passenger side stake pocket, and ran the coax under the lip of the bed, through the knockout in the bed toward the cab, and passed it through an existing grommet that is behind the rear passenger seat, pull the carpet wall back, poke through. (And deal with black goop). That gets cable into truck for antenna.

Next.. the simple part, power. I decided to tie my ham radio to up fitter 1.. it's fused, I can flip it off when needed, I don't want it on an 'always on' (and my last 2 switches are already configured for always on, for my e-ink license plate that hooks into them. I put it on an up fitter so I can kill the LTE radio when I feel like).

Now, re-posting some facts about upfitter wiring, since there are a million posts about it and most tell you to read a bunch of other places:

On a 2021 F250, the upfitter wires come straight from the upfitter fuse box, in the engine compartment, passenger side. It's easy to push the two clips and pull the small fuse box up, and you can remove the black tape, and all of the upfitter switches are there and labeled. By default, none of them are 'always on', you have to move a fuse in that small box to change that, read your manual. Switches 5/6 can be made always on, but they are also your fatter 2 cables and higher amp. For some electronic noobs, there is no 'negative wire'. Your device will take power from one of those upfitter wires, and your return wires goes to ground (ie, your frame, not back to the upfitter wires.

Now, where are the 'upfitter wires' in the cab? Technically there aren't any. There are pass-thru wires, which are literally a couple feet of wires, cut off on both ends, that run through the firewall. On the inside of the cab, you move the small panel by the passengers right foot.. you'll see a bundle of PTO wires, those are *not* your pass thru wires. Your passthru wires are *not* bundles with those wires. Every wire in that bundle goes back to a connector, which isn't pass-thru. If you find the most uncomfortable position you can get your body in (head to the floor, flash light up) and peer up into the darkness behind all the bundles of wires.. you should see a 4 wires going into a single taped/cap. Those are your pass thru wires. No, they don't get any longer. To actually attach to them, will be a pain in your butt.

Now, where are they on the other side of the truck, in the engine bay? In my 2021 F250 Tremor, you can not see them at all from above the engine bay. You can't see them at all laying on a creeper under the truck either. My average male hands/arms also can't reach around the batteries and fuse boxes and touch them.

I had to break out a scope camera to actually find them, the 4 wires are annoyingly tapes to another loom, under the main fuse box relay. These are also, generally not long enough to actually wire anything to without disassembling the truck. (You then have to run a wire from the pass-thru, to the wire you want to use from your upfitter bundle. These actually DO reach each other, if you take apart your truck).

With that said, here are six simple ways to access the blunt cut pass-thrus:

1. Don't order a truck with wheel well liners. Turn your wheels to the left, pop a Motrin, get on your creeper, and wheel under the truck.. Reach up with a knife, cut the wires loose. You can now touch the wires. You won't really be able to actually wire to them. (You may also be able to just reach over your tire. I don't know, removing my existing wheel well liners looked like a 'it'll never be the same' situation)

2. Blow up your engine. When Ford has your engine out of the bay to replace it, they will likely have also removed your battery, battery tray, and fuse boxes. At this point, you can reach the blunt cuts and wire what you want.

3. Go to MIT and get a double degree in robotics and nano technology, invent little nano robots that can carry wires and solder for you.

4. There is no simple way.

5. There is no simple way.

6. There is no simple way.


In the end, I ended up running a wire from the up fitters, over the wheel well, along the body and came in behind the cab where I had the antenna enter. It's not ideal to have power parallel to antenna cable, but I didn't really want to cut the existing grommet in the truck bay, even though that seems to be what just about everyone else ends up doing.


Hope this helps!

Happy weekend folks :)
 
There is a simple way :ROFLMAO:

My father did my wires into the cab last weekend while i was visiting (he did his the day before) and had my wires run in maybe 30 minutes total. Link to his post on another forum. All i have to do now is install the wiring up the pillar to my mirror for my radar detector but all prepped and easily ready to go now.

 
There is a simple way :ROFLMAO:

My father did my wires into the cab last weekend while i was visiting (he did his the day before) and had my wires run in maybe 30 minutes total. Link to his post on another forum. All i have to do now is install the wiring up the pillar to my mirror for my radar detector but all prepped and easily ready to go now.


Couldnt tell which part of that post was related to yours, or if it was saying something just changed on the 2022?
On the 2021 even via the door side panel (where the vent is), you still can’t reach those wires. Even a child’s hand wouldn’t be able to reach around the framing. Can only reach via the bottom.

and the wires in mine are under the main battery tray, not reachable by a normal human hand once the relays for the upfitters are unclipped.


will stand by there is no easy way on a 2021 diesel tremor with well liners.
 
In my first 2021 Lariat Tremor these wires were exposed and easy to access. In my current 2021 Platinum Tremor, I tore apart half the harness only to realize that the wires were not there. I ended up running my own wires.

I know the price of copper is rising, maybe Ford is trying to save a few bucks to maintain a decent quarterly earnings due to the chip shortage fiasco... ?
 
I read on another Ford trucks forum that the wires can be accessed easily by pulling the panel on the side of the dash (the panel hidden by the door when the door is closed). I can't confirm but maybe someone here can check and report back.
 
I read on another Ford trucks forum that the wires can be accessed easily by pulling the panel on the side of the dash (the panel hidden by the door when the door is closed). I can't confirm but maybe someone here can check and report back.

They are. That's how both mine and my fathers trucks were done inside the cab. Both 2021's.
 
There is a simple way :ROFLMAO:

My father did my wires into the cab last weekend while i was visiting (he did his the day before) and had my wires run in maybe 30 minutes total. Link to his post on another forum. All i have to do now is install the wiring up the pillar to my mirror for my radar detector but all prepped and easily ready to go now.

Sorry to bump an older thread, but this one and the one linked here are getting me closest to wiring up a dash cam and high idle to the upfitters in my 21 F-350 Lariat (not a Tremor, hope that's OK). Posting here, wondering if anyone sees something easy that I'm missing?

I found the pass through wires in the interior, but I don't see any way to make use of them with how short they are. Tried pulling them a bit, but they wouldn't budge and I can barely get my fingers on them from every direction I tried.

20230509_200449.jpg


I'm also not seeing the exterior pass through wires. Hoping to avoid pulling the battery or wheel well liner.

20230509_182543.jpg
 
I am miles from my 2022 right now or I would send pics but I just went through this last month. You need to pull the small relay box up (the one on the right in your second pic) and carefully lay it to side. You should see them wrapped in tape and doubled back on themselves which makes them almost invisible. There is a "wiring label" wrapped up in the loom so be careful not to cut or tear it. I used butt connectors form my wires but may go back and put single pin Weather Pack connectors on all the wires to facilitate swapping switch positions easier.
 
Sorry to bump an older thread, but this one and the one linked here are getting me closest to wiring up a dash cam and high idle to the upfitters in my 21 F-350 Lariat (not a Tremor, hope that's OK). Posting here, wondering if anyone sees something easy that I'm missing?

I found the pass through wires in the interior, but I don't see any way to make use of them with how short they are. Tried pulling them a bit, but they wouldn't budge and I can barely get my fingers on them from every direction I tried.

View attachment 119975

I'm also not seeing the exterior pass through wires. Hoping to avoid pulling the battery or wheel well liner.

View attachment 119974
mine are like this except behind the metal bracket and cant move them either lol
 
mine are like this except behind the metal bracket and cant move them either lol
I watched about every video I could, and didn't see anyone who had their interior wires stuffed up there like that. I don't see how they're even usable. Looks like I might have to run my own like it's 2003 lol.
 
I watched about every video I could, and didn't see anyone who had their interior wires stuffed up there like that. I don't see how they're even usable. Looks like I might have to run my own like it's 2003 lol.
I just did my high idle and a dash cam, so I just went through this.
Here's how I did it, if it helps

Pulling the fender liner is the easiest way to get to the wires in the engine bay.
For the interior, I pulled the passenger fusebox, like in the video.
It still wasn't 'easy', but it made getting to the interior wires 'doable'.
 
I just did my high idle and a dash cam, so I just went through this.
Here's how I did it, if it helps

Pulling the fender liner is the easiest way to get to the wires in the engine bay.
For the interior, I pulled the passenger fusebox, like in the video.
It still wasn't 'easy', but it made getting to the interior wires 'doable'.
Very helpful, thank you. We travel full time and I'm working on this at a campground. I was excited to see all the videos where it looked a lot easier than tearing the truck apart and drilling holes. I guess not. :LOL:

I'm glad Ford seems to have learned and made it a bit easier on the 22s.
 
I just did my high idle and a dash cam, so I just went through this.
Here's how I did it, if it helps

Pulling the fender liner is the easiest way to get to the wires in the engine bay.
For the interior, I pulled the passenger fusebox, like in the video.
It still wasn't 'easy', but it made getting to the interior wires 'doable'.
Actually, after reading through your thread and how you did it...how much to do mine? :LOL:
 
Very helpful, thank you. We travel full time and I'm working on this at a campground. I was excited to see all the videos where it looked a lot easier than tearing the truck apart and drilling holes. I guess not. :LOL:

I'm glad Ford seems to have learned and made it a bit easier on the 22s.
ok, I'll say this, if you are "on the road/working at a campground", it would be far easier to just drill a hole in the firewall and run all new wires.
 
ok, I'll say this, if you are "on the road/working at a campground", it would be far easier to just drill a hole in the firewall and run all new wires.
It's looking that way. I really hate that there are these "convenient" wires so I don't have to drill through the firewall, and I'm going to end up drilling through the firewall because Ford saved $0.17 in wiring.
 
Following to remind myself to look here, and at the comedic post. =)
 
Yeah my 2022 was super easy for exterior additions. The upfitter pig tails were right under the fuse box connected to the battery box. I just pulled the fuse box up, flipped it over and wired my extra fogs to the switches I needed. Super easy.

Getting wires through the firewall to connect to upfitter switches is a different story. I wired some tow gauges in not too long ago and added their own dedicated fuse box. I took the passenger battery out, took the fuse box out, took off the connectors to my ecu, all so I could gain access to the big rubber harness grommet in the firewall. Ford did put in an extra, empty exit through this big grommet so I ran about 10 wires through this grommet using a straightened coat hangar, then wired the 4 i needed and rolled the other 6 up and tucked them behind the glove box. I also zip tied the ends of the wires and tucked them behind the fuse box under the hood. That way if I ever need to run wire through the firewall again, I just tie the wire I need to one of the wires I ran, pull the wire through one side or the other, and I can easily pass my new wire through the fire wall for whatever I need. (y)(y)(y)(y)(y)
 

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