So I would like to find out what equipment is needed to reprogram a gem yourself. Could someone help me figure out how it works? Also preferably a way of understanding how the components in the controller work as well. I have some soldering experience and experience with an Arduino and a pi doing some little projects with h bridges and the like. Dehumidifier broke and I used an Arduino to make it work with some relays. Looks like crap but 
point being I really want to understand how they work and how to reprogram them.
Is this a theoretical project?
Or do you actually have a car that you would like to get into and play with?
What year would that car be?
Better yet, if you can get a glimpse of that barcode on the controller and right above it is a big long number. Pick off the last two digits and report back with your findings.
(Hint- it will end with a T1, T2, T3, T4, or maybe even a T5)
Unless it is a really new car (2016-> newer) then there is not much you can do with those because they are locked up fairly tight and it is easier to replace them.
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so if i get a 2002 gem car how would i reprogram it to go faster then if i cant program it? how is it done by the services that reprogram them? its a theoretical one i want to buy.
Sw is almost free. Then you need a usb to ??? depending on the controller.
I can make you one if I know what controller you have.
Or just put a magic magnet on it to remove speed limit.
What software do you use? And what different ports are there? And how does it communicate?
Jat- This is an excellent time to introduce you to the search tool.
Find the magnifying glass in the upper right of your screen and enter the keywords
“GE Sentry”
This will lead you to several conversations on the same topic.
Softly and slowly. In romance languages sometimes if you ask it nicely.
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I happen to have my old programming cables in a desk drawer next to me
t1 controller - USB → serial port → whatever this converter board is → 23 pin port in the controller
T2 controller - USB → serial port → harness from serial to 12 pin connector → 12 pin port in the controller.
I run sentury software on a windows laptop for both controllers. Haven’t messed with t3-t5 so can’t help there.
Playing some Al Green while connecting the laptop to the controller helps with a better connection 
So what are those individual cables called that your using to communicate? I found a download of ge sentry. Looks like USB to serial of some kind, the just a 9 pin serial extension, then serial to ???.
Am I correct about the USB to serial adapter? Is there one in specific that works well for this? And is that a db9 cable? Is it female end to female end? And also what is the connector called that it is adapted to? And what pins of the db9 ended cable go to what pins of the ??? ended cable?