Adding Third Key via Forscan

[WhooptieDo]

So after weeks of attempts, amazon fob, and now a genuine OEM Mustang FOB, I haven't been able to program a third key to the car. I am attempting to add a remote start key to a bare bone base 2025 Ecoboost 100A. I've bounced around with the 2 key in the slot trick, tried every variation of it that I can think of, it wont work. The freq's are right but somewhere, I think this simple procedure is just plainly disabled.

So now I'm moving on to Forscan. I'm no stranger to Forscan, I've used it and experimented for years.... however I have never gone into the PATS programming for any of my vehicles. Every bit of searching I've found tells me that I have to erase all the keys in order to add a third, but this doesn't really make any sense to me. I'd rather not erase two good keys and risk a perfectly good system, at minimum make me sweat when something fails.

Has anyone simply added a third key via Forscan before? Or does anyone have any other input to get the basic procedure from the manual to work?

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[DT-GT]

I added a third FOB to my 2025 GT. I must have tried it 20-25 times on different days with no luck. I gave up for a week then tried again. Failed several times then it worked. I don’t think I did anything different. So thinking that timing in critical. Good luck!

 

[WhooptieDo]

I added a third FOB to my 2025 GT. I must have tried it 20-25 times on different days with no luck. I gave up for a week then tried again. Failed several times then it worked. I don’t think I did anything different. So thinking that timing in critical. Good luck!

I'm right there with you. I just haven't had the luck. Do you have any tips on the timing? According to the Mach-E forums it's critical as well.... then some guy followed up with "I finally gave up and gave it only a second between key swaps and it worked!" Doh. Theres so much conflicting information. I found two other tidbits saying "Don't have the phone in the car" and "Make sure the doors are locked first". I'm also kinda wondering if it has something to do with being a 100A car.

My laptops charging up regardless right now, I got my extended license on forscan now, so I'm gonna have some fun tinkering regardless.

 

[DT-GT]

I have Forscan but did not try this method. Did the same every time. But perhaps I was quicker on the timing. In fact, I was shocked when it finally succeeded.

 

[WhooptieDo]

I have Forscan but did not try this method. Did the same every time. But perhaps I was quicker on the timing. In fact, I was shocked when it finally succeeded.

So this is actually crazy, but I just got the programming procedure to 'work' right now. It said new key programmed on the dash, got the flash of the lights and everything. The difference this time was I did it 'a little quicker' and I kept all the keys in the same cubby as the backup slot.


annnnddd the key doesn't work, at all. So now I'm confused, and I can't seem to reproduce the procedure lol

 

[DT-GT]

That’s really strange. After mine confirmed programmed, just like yours did, mine worked fine. STRANGE!
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So this is actually crazy, but I just got the programming procedure to 'work' right now. It said new key programmed on the dash, got the flash of the lights and everything. The difference this time was I did it 'a little quicker' and I kept all the keys in the same cubby as the backup slot.


annnnddd the key doesn't work, at all. So now I'm confused, and I can't seem to reproduce the procedure lol

 

[WhooptieDo]

okay, I FINALLY figured out how to repeat the procedure. I can do it almost consistently now.

KEY IN SLOT
Hit start button, 2 seconds, then OFF
within 1 second, swap the keys

The procedure works every time with those timings. I actually tried it with the amazon key I had, the first time it said "Key Program Failure". The second time it said "key program successful"

Neither of my remote start keys work. None of the buttons.

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