Chosen Solution
I have replaced the keyboard and keyboard backlight on this machine. The backlight comes on. BUT, now the replacement keyboard will not register most letters and numbers. Many keys will cause a system clunk sound when pressed. I have to connect an external keyboard to log into my account. Since the keyboard will not register letters properly, I cannot do CMD-OPT-P-R + Power Button to reset the NVRAM, of start with D held down for hardware test. Is it possible that the keyboard requires a different firmware version than the one on the machine? This machine is running OSX 10.5.8 (I have not upgraded because I have a ton of costly software on it. One 3D modeling and rendering package is not in existence anymore. It is a good program, so no upgrade to OS)
Reseat your keyboard cable, see step #18 of this guide. I use a piece of electrical tape on the cable to pull it into the slot rather than trying to push it in. Be aware of how the lock works before doing this. MacBook Pro 15" Unibody 2.53 GHz Mid 2009 Upper Case Replacement
I opened up the case and found the keyboard cable at a slight angle in the slot. However, reseating it and closing the case up and starting showed no improvement. Using electrical tape on the ribbon cable to seat it in the socket was a great suggestion. The socket has a lever that has to be released to allow insertion of the end of the cable. The lever is pressed back down into place when the cable end is inserted properly. Attaching this cable IS difficult. I initially had put a bit of a bend in it to get some pressure on it to get it guided into place in the connector. I am aware that bending a ribbon cable is NOT a good idea, but it seemed the only way to get some push on it in the direction of seating. There is another issue with the keyboard itself which may or may not be important: There are 51 SHORT, TINY screws holding the keyboard onto the top case. I managed to loose 2 of the screws. One may still be logded inside of the exposed cavities inside the keys. Don’t know if I was able to get it out by turning the machine over and bumping it against my towel covered work table.
