I’m trying to wire my GPS into my SD using an Upfitter switch. Had no problem with my 2017 SD but no such luck this time. Using Upfitter 2/violet-orange because 1 is wired to my aux fuel tank pump. That was done by a local dealer & works fine but he didn’t use the pass thru wires instead he wired to the green-brown wire under the hood & took it over & ran it thru on the driver side. My process was to connect the violet-orange wire under the hood to the battery & then I connected the pass thru v-o in the foot well to the lead from my gps. I attached the ground wire to a bolt in the passenger foot well underneath the top edge of the carpet. Nothing. I double & triple checked all my connections & the only one that concerned me was the ground but I was unsure how to test. I tried running a jumper to the negative post on the battery. Nothing. Used a 12 volt test light & have 12 volts out of the battery & at the wire entering the fuse box but no voltage at the wire in the foot well. Pulled the 25 amp fuses & they all looked good. Not sure where to go from here. One thing I noticed is there is no green/brown wire in the foot well. It should be there for Upfitter 1. There are 14 wires which is the correct number. Makes me wonder if the wrong plug in was used with different color codes. Maybe I should test each pin for current. Thoughts? Thanks!

 

Have you tested continuity on any of the wires?

 

Upfitters already have power, no need to connect to the battery.

 

So looking back at this, the upfitter wires don’t pass through the firewall directly. The upfitter wires are under the fuse box. Then my pass through wires were taped to another bundle directly behind that box. I have not seen a color code chart for the pass through wires because it seems not everyone has the same color wires.

So to be sure, you have the upfitter wire connected to one of the pass through wires correct under the hood, correct?

 

Are you sure? I think the reason for pass thru wires is to connect a device in the cab to the engine bay area to connect to power. That’s the reason the fuses are there so when you connect to the battery via the pass thru wires under the pass thru fuse box you have fused power to the cab.

 

No but thanks for suggesting. I’ll look for a video on how to do that.

 

He is correct. There are upfitter wires that already have power. If you connect to one of those there is no need to connect to the 12V.

The pass through wires are just that, they pass through the firewall and are connected to nothing on either side. You need to either connect it straight to 12V (preferably fused) for an always on connection, or connect it to one of the upfitter wires so it can be a switched power source.



These are the upfitter wires and their wire mapping to the upfitter switches

 

The color code chart for the pas thru wires is in the owners manual. Since my truck is missing the brown/green wire in the cab it makes me question the accuracy of that chart.
Yes, I’m connected to the violet/orange wire under the hood that goes into the fuse box before passing thru the firewall into the cab.

 

Copied from another forum…
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.




So you are connected to one of the upfitter wires?

The upfitter wire is then connected to one of these pass through wires that were taped to the wire bundle? These go through the firewall and should be located under the dash on the passenger side.

 

I am connected to an Upfitter wire under the hood. This I know because I am connected to the violet/orange wire & it reads 12 volts when the ignition & Upfitter 2 are on. When Upfitter 2 is off it reads no voltage (ignition on). However I probably have selected the wrong bundle in the passenger kick panel area. That would explain why there is no green/brown wire. Thanks, ill check further.

 

I looked again & couldn’t see or feel anything else so I pulled I unplugged the end of the wiring harness I’ve been attempting to wire into & got the part #SC3T-14A303-CB & did a search. What came up was PC3T-14A303 Upfitter Wiring Harness which is what the other part plugs into. So I’m back to believing that I was on the right track to begin with. So since no voltage is appearing in the kick panel area I’ll test the continuity or run a jumper to try to see if the problem is in the wire. 🙁

 

I took a minute at lunch and went back out to my truck. I removed the carpeted panel on the passenger side, just under the glove box. When I did so I had to disconnect the light wire. The pass through wires were wrapped around it and taped pointing back up. The other wires were the PTO wires.

 

You got the wrong wires, that harness (SC3T-14A303-CB) is for the Upfitter Integration System, you are looking for a bundle of 4 wires. Have a look at this thread: https://www.ford-trucks.com/forums/1...res-found.html

 

I looked at the instructions for my test meter & it said don’t test a live wire. I could disconnect the battery. Not sure what I’d lose if I did that.

 

Yeah I saw that. Pulled the panel off under the glove box already. Got down & looked up into the area they’re supposed to be. Got my hands up in around where I couldn’t see. Nothing! SH-T! I’m really really getting aggravated! Just hooked it up to a PTO for now. Maybe I’ll look again tomorrow. I’ve already spent over 8 hours on this BS! Did I mention I’m p-ssed?