In your protractor.configuration file, if you have the following: 
capabilities: {
    'browserName': 'chrome',
    'chromeOptions': {
      'binary': 'path/to/chromedriver.exe';
    }   },
Then please remove that binary and instead point to the chromdriver like this: 
//protractor.conf.js
chromeDriver: "C:/path/to/chromedriver.exe",
capabilities: {
    'browserName': 'chrome',
    'chromeOptions': {
    }
  },
Notice how I removed the 'binary' argument from the capabilities and added the "chromedriver:" attribute.
That worked for me in removing that annoying error that says "
    UnknownError: chrome not reachable
        28-Jul-2016 10:16:57      
    (Driver info: chromedriver=2.19.346078 (6f1f0cde889532d48ce8242342d0b84f94b114a1),
platform=Windows NT 10.0 x86_64)
 (WARNING: The server did not provide any stacktrace information)
Lastly makes sure you update both chromedriver and seleniumServer like this: 
webdriver-manager update
OR 
Run this command below to update to a SPECIFIC chromedriver version i.e v2.24 as of 10/04/2016: 
webdriver-manager update --versions.chrome 2.24
if it says that the command is not recognized, then add it to your PATH in windows environment variable. The webdriver-manager generally sits in the Protractor folder which you can get with npm install protractor