Computer

It comes out from the engine side.

Yes, it does have to be programmed in the vehicle before it will run.

How difficult is that to do. Is it possible I can do that myself using my laptop? Do you know of any videos that explain how to program the computer?

No, you can't program. Mosty repair shops can't even do that.

That doesn’t make sense. Then how do you program a new ECU / ECM?

You first purchase a $10,000 scan tool. You then pay a subscription fee to the manufacturer to have access to the software and then you go to some very advanced training to learn how to do it without locking up the computer.

That’s insane! Do dealerships have the equipment and know how to program them? I’m guessing you would have to get a second mortgage on your home to pay for it.

Yes, the dealers all do that and the average cost is about $100. Even when most independent shops replace a computer, they have to tow it elsewhere to have it programmed.

If there is something wrong with the ECU / ECM. Is it possible that cold weather could cause problems?

I have no idea what issues you have with your car or computer. Like any electronic circuit board, the computer can be effected by temperature changes, but even if it is, that is still a defect in the computer.