Common Lenovo T420S Issues - Unexpected Shutdowns, Freezing and Lag and others

I recently  had the riveting role of setting up a ton of Lenovo T420s laptops and Dell Vostro's and have prepared this post to solve a lot of issues you may face with your Lenovo T420S laptop.

1. Unexpected Shutdowns, Random shutdowns when away from computer

The first one is an unexpected shutdown issue with the lenovo t420s , whenever you are away from the machine for an hour or more it will shutdown unexpectedly and start a start up repair when you next boot up the machine.

Cause

The cause of this issue usually relates the  Lenovo Rapid Boot software installed on most of there newer laptops, uninstalling this software will usually resolve the issue. If not you can try a bios update through system update. (quick update , had one with random shutdown's turned out to be a faulty motherboard , just in case your trying to fix it in vain.)

2. Laggy Screen or Delay when using keyboard and mouse

This is another common one, if you find that when you drag the mouse across the screen you notice a lag every 5-6 seconds or that when you type it doesn't appear instantly you can try the following

Cause

The most common cause for this issue I have seen are dodgy Bluetooth drivers, for some reason an older version of lenovo's Bluetooth drivers caused a lot of hanging and lagging issues almost like it was paired to a Bluetooth device that was slightly out of range.

 There could be a more straight forward reason for this but turning off the bluetooth Fn + F5 , or just switching off the wireless with hardware switch usually works.  You can also update your bluetooth drivers but they often hang during installation. (update : Turns out the most common cause of this issue is a dodgy motherboard,I've had about 5 replaced so far )


Hardware Related Issues

I've also had a few hardware related issues which may help you diagnose your issue

Noisy Fan - Very common with the t420s or any slimline lenovo laptop, Replace FAN call lenovo

Wifi won't work - Switch broken or not connected properly , call lenovo fix motherboard connection

Laggy Mouse and Keyboard - motherboard , keyboard and palm rest was replaced in my case

Computer Super slow - Run a hard drive diagnostic test from the bios, possible dying dead hdd

I shall add more as appear, feel free to ask a question about any issues you've had most likely I've run into them as well.