Understanding Ford GEM Wake Up Diagram
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=120674
Printed Date: May 14, 2025 at 2:30 AM
Topic: Understanding Ford GEM Wake Up Diagram
Posted By: jetblue
Subject: Understanding Ford GEM Wake Up Diagram
Date Posted: March 11, 2010 at 11:48 PM
I'm not understanding this quite right and would like a little help understanding how wiring this relay is going to wake up the GEM on my Ford F250. My understanding of this relay's purpose was to pulse the door ajar wire to "fool" the vehicle into sensing that the driver door had been opened. This relay does not seem to do that. All this relay appears to do is break continuity on the door ajar circuit when pushing the alarm unlock button. Would it not make sense to plug the RED wire in the diagram into 30, the BLUE wire into 87A and then run the YELLOW wire to 12V constant? At rest, connectivity on the door ajar circuit will be unbroken for normal driver door sensing. But when you push the alarm unlock button, that would send 12V momentarily to the GEM module. How am I doing? Certainly the smart guys at DEI wouldn't come up with a diagram like this if it would not do the job. 
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Replies:
Posted By: howie ll
Date Posted: March 12, 2010 at 2:33 AM
Hope I'm on the right track here but bloody Ford door contacts work the opposite to everyone else's!
When the door is shut, the wiring goes to ground.
When the door is opened, the wiring goes open circuit. That's exactly what this relay is doing.
Posted By: oldspark
Date Posted: March 12, 2010 at 3:41 AM
Aha! "Fail-safe" wiring. How refreshing.....
Posted By: Ween
Date Posted: March 12, 2010 at 6:11 AM
check to be sure your vehicles GEM shuts down. roll the drivers window down, lock the doors with the factory remote...or lock button on the door. shut the door if it's the latter. wait a few minutes..3-5. reach inside the open window and press the unlock side of the door lock switch. if the doors unlock, you're fine. if they don't, you need to wake up the GEM. make sure the door latch wire is being interrupted, you don't have to use the driver's door, any door latch will work. m
Posted By: mustyk@att.net
Date Posted: March 12, 2010 at 7:26 AM
Howie II is correct, the NEWER Ford vehicles work opposite then what we have seen in pin switch wiring for the past 30 years so that diagram IS breaking the circuit to wake up th GEM!! ------------- thetopinstaller
Posted By: mustyk@att.net
Date Posted: March 12, 2010 at 7:30 AM
P.S. to howie II: You seem to know alot about US vehicles over there across the pond . Do you work with alot of them? Or are all the vehicles very similar these days?
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thetopinstaller
Posted By: howie ll
Date Posted: March 12, 2010 at 12:14 PM
Nope, did a Ram last year,an F150 the year before but they're as rare as rocking horse s**t!
It's just that we've had the gem box for about 11 years, I'm fully familiar with its problems, the directed 1076 fix etc., also English Fords had the hood switch as an open circuit from the early 80s.
Ford Focus/Mondeo essentially the same as US Focus/500, though the Euro and US Focus diverged in 05, they are coming together again next year.
Euro GM, Opel/Vauxhall are about as different as you can get, the wiring is nearer to VW!
Having said that they do share some, Astra =Saturn Astra, Insignia = Buick Regal.
US Honda Civic completely different from UK made version, the Corolla doesn't exist,it's an Auris and we had the UK made Yaris 4 years before you.
Posted By: Twelvoltz
Date Posted: March 12, 2010 at 5:46 PM
The method described above is the 'correct' way to wake the GEM as it makes the vehicle think the door is open and wakes up. However the GEM wakes up when you energize the ignition as well. Even though I will probably catch a bunch of slack for this, I am still going to post it. Maybe someone out there knows if it will cause vehicle problems with the new Ford vehicles. But I can say this works fine on 01 Fords without any other problems (my personal truck), as it has been working since 2001.
Quick, dirty, and possibly harmful Ford 'GEM wakeup' method...add one relay, pulsed by factory alarm disarm output to the vehicle ignition wire, set the keyless unit to double pulse unlock.
Wired Like:
85 and 30 to fused +12V
86 output from system's negative FAD
87 output to ignition circuit in vehicle
Yes, this will turn on the ignition for a second EVERY time the FAD wire is activated. The doors will unlock on the second unlock pulse.
Once again, I do not know if this will cause any vehicle problems either. I am simply posting another way of waking the GEM.
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Installer, IT support, and FFL. I need less hobbies.
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