Lenovo ThinkPad S431 Hardware Maintenance Manual page 47

e. memory module on the upper memory slot, if there is one
f. Optical disk in the optical drive
g. PC Cards
4. Turn on the computer.
5. Determine whether the problem has been solved.
6. If the problem does not recur, reconnect the removed devices one at a time until you find the failing FRU.
7. If the problem remains, replace the following FRUs one at a time (do not replace a nondefective FRU):
a. System board
b. LCD assembly
.
Chapter 4 Related service information
41