I have a family members Macbook Pro 2013 (a1502)
They had a water spill on it and it worked for a couple of days after the spill
and then it wouldn't turn on, so naturally they then gave it to me!
Long story short, replaced the keyboard, it booted up and worked briefly and then trackpad and keyboard just not responding. Weirdly the keys along the outside of the keyboard such as ESC, CAPS, SPACE etc didn't work, but all lettered keys were working. Thought perhaps I just got a dodgy keyboard so sent it back and installed the new one. Worked fine for a couple of restarts and then the same issue, keyboard just not responding, and trackpad not responding (it was luck of the draw after a restart if they wanted to work or not). If I plugged in an external mouse and keyboard there were no issues, and managed to reinstall to the latest big sur os.
After numerous reboots the keyboard and trackpad works intermittently on startup. Decided to replace the logic board, exact same problem.
So the following have been replaced:
Keyboard
Logic board
The cable that connects the wifi board to the logic board (found the clip to be loose so replaced it).
So the only things not replaced is the trackpad, wifi board, battery and speakers.
To isolate I unplugged the trackpad and booted up, keyboard still not working. So plugged trackpad in and unplugged wifi board, keyboard still not working.
My only other conclusion, the trackpad is faulty, and when I replaced the keyboard the second time I originally plugged it into the first logic board which could have been water damaged thus making this new keyboard faulty also. It's just strange to me that the trackpad and keyboard either both work, or both don't work, it's never one or the other.
Not too sure where to go from here, if it wasn't a family member I wouldn't have gone this far down the rabbit hole.
They had a water spill on it and it worked for a couple of days after the spill

Long story short, replaced the keyboard, it booted up and worked briefly and then trackpad and keyboard just not responding. Weirdly the keys along the outside of the keyboard such as ESC, CAPS, SPACE etc didn't work, but all lettered keys were working. Thought perhaps I just got a dodgy keyboard so sent it back and installed the new one. Worked fine for a couple of restarts and then the same issue, keyboard just not responding, and trackpad not responding (it was luck of the draw after a restart if they wanted to work or not). If I plugged in an external mouse and keyboard there were no issues, and managed to reinstall to the latest big sur os.
After numerous reboots the keyboard and trackpad works intermittently on startup. Decided to replace the logic board, exact same problem.
So the following have been replaced:
Keyboard
Logic board
The cable that connects the wifi board to the logic board (found the clip to be loose so replaced it).
So the only things not replaced is the trackpad, wifi board, battery and speakers.
To isolate I unplugged the trackpad and booted up, keyboard still not working. So plugged trackpad in and unplugged wifi board, keyboard still not working.
My only other conclusion, the trackpad is faulty, and when I replaced the keyboard the second time I originally plugged it into the first logic board which could have been water damaged thus making this new keyboard faulty also. It's just strange to me that the trackpad and keyboard either both work, or both don't work, it's never one or the other.
Not too sure where to go from here, if it wasn't a family member I wouldn't have gone this far down the rabbit hole.