I've got a 2021 Super Duty Wiring Diagrams book on order, but it's going to be a few weeks before I have it on hand. Does anyone have access to the PCM pinout for 2020-21 F350 7.3L Gas? From what I gathered things changed slightly from 19 to 20.

 

What specifically are you looking for? The PCM has many connections and the diagrams cover many pages.

 

Looking to find the wires for both the starter relay and the fuel pump relay. Thanks!

 

These are from 2020 manual. The formatting is kinda garbage as a lot of the connector numbers overlap the pin numbers. Let me know if you have any questions or need clarification.

 

This is great! Thanks. I have the dual battery, but I assume that only changes things slightly on the battery side, not the PCM side. Do you know if these diagrams indicate which plug on the PCM they describe? I believe there's a small, medium, and large plug on the back of the PCM in the engine bay passenger firewall.

 

There are 3 PCM plugs: C175B is 90 pins, C175E is 126 pins, and C175T is 90 pins. The connector referenced in both drawings is C175B.

 

Where do you guys buy your manuals from? I prefer physical copies if possible.

 

I got mine from ebay. I prefer electronic as you can search them and quickly navigate where you need to go. If you need physical copies you can always print pages you need.

 

Fair enough. I'm so used to using printed books, especially wiring diagrams. I guess I'm set in my ways, and I'm only 37! lol
Do you have official Ford literature or third party?

 

You can find these on ebay or the web here: https://www.factoryrepairmanuals.com/
I found a new Wiring Diagrams book on ebay for about $30 cheaper than online.

 

Perfect! Exactly what I was looking for. Thanks again!!

 

I bought them from ebay and they come as PDF on a CD, and I'm pretty sure all the information is official Ford documentation. Though with the Ford system I think they have everything on a website and there is hyperlinks to other procedures and diagrams. In the PDF I got, the links don't work so you have to navigate to other procedures or diagrams yourself. Oh well, it was pretty cheap and the information has proved valuable to me.

 

So I gave this a test run by cutting the gray wire with the orange stripe on the left plug of the PCM assuming this would prevent the starter from firing. Unfortunately the truck started up just fine.

I thought perhaps I misunderstood the plug layout and the C175B plug is on the right, even though in the diagram above it appears the plugs are shown as they are on the firewall from left to right. Anyway, I cut the grey wire with the orange stipe on the right plug with no effect to the starter relay either.

I'll be soldering these connections back together and doing some more research. Does anyone have any insight here based on the wiring diagrams above as to why cutting the GY-OG wires had no effect on the starter?

 

Interrupt the ground on push button start.
no bueno.
pita to get to.
is one easy way vice chopping wires

 

I’ve got a keyed ignition, but the concept with it may be similar as you’re aiming at here, thanks.

At this point I’m too curious about why the PCM GY-OG cut failed. I’d like to understand that before abandoning plan A. According to the diagram that should be a clear interruption of the starter relay circuit… unless I’m missing something.