if you use Grid, you need to configure the Chromedriver executable in node :
java -jar selenium-server-standalone-2.31.0.jar -role node -hub http://localhost:4444/grid/register -maxSession 15 -browser browserName="chrome",version=ANY,platform=WINDOWS,maxInstances=15 -Dwebdriver.chrome.driver=lib\chromedriver.exe
The most important part is the switch -D, which comes immediately after setting up the Chrome browser.
also, if you use multiple nodes, this path should be directed to the chromedriver executable on a specific computer (node). That's why I have it as a relative path, and not as an absolute path ...