Can I replace my ecu (not the relay but
actual "brain" with a previously used one?
And if so is there a proceedure or steps
necessary to do so?
Yes it can be replaced,but make sure it matches your ECM numbers,if numbers dont match it will have to be flashed to your car.
I replaced my ecm with macthing numbers and my car is still not fireing so Idk if that's true and I know the ecm is good
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