This is what the service manual for your computer suggest.
Check 1 Make sure the keyboard cable has been firmly connected to the system board. Keyboard System board CPU If the cable is loose or off, reconnect it firmly and return to Procedure 1.
If there is still an error, perform Check 2.
Check 2 The keyboard may be faulty. Replace it with a new one following the instructions in Chapter 4. If the problem persists, perform Check 3.
Check 3 The System board may be faulty. Replace it with a new one following the instructions in Chapter 4. If the keyboard is still not functioning properly, perform Check 4.
Check 4 The memory may be defective. Replace the memory module with a new one following the steps described in Chapter 4. If the problem persist, perform Check 5.
Check 5 The CPU may be faulty. Disassemble the computer following the steps described in Chapter 4 and replace the CPU with a new one.
So now where all those steps are listed, here are the instructions for the keyboard removal and the service manual is available right here. Good Luck