What does the code PE mean ? - LG WM-2077C Front Load Washer

In some LG's I have 'PE' as 'pump/pressure error/fail' (probably blocked filter) and I am guessing that in yours 'PF' decodes as 'pump fail'.

I would gently suggest as a first step that you clean the drain motor lint tray/filter. So many 'faults' are caused by blocked filters and many machines will not even go to spin or release the door lock if there is any water still left inside.

Here are my guidance notes for checking both the drain motor filter and the drain motor ;-0)
If you are unsure where the filter is, it is often behind the front lower (kick) panel (or in some machines at the rear in an awkward position!) and most are held in by a round cover/knob. Sometimes the filter will not come out with the cover and you will have to persuade it to come out to play!

REMOVE POWER AND ENSURE YOU HAVE A WATER RECEPTACLE/RAGS TO SOAK UP THE WATER WHICH IS BOUND TO POUR OUT!
It's surprising what people have found in theirs! It is always worthwhile checking it on a regular basis.

Now- whilst the filter is removed it is normally possible to see the drain motor and ensure it is not jammed by a foreign object such as a needle or a toothpick. It should be able to be turned by hand/finger- the power IS OFF!

At this point it is also possible to test if the motor works. No clothes or water in the machine, select a spin cycle and put the power back on. You should be able to see the motor turning at some point, possibly straight away. If it doesn't work then the motor is malfunctioning!

Hope helps.

PE indicates PRESSURE SENSOR ERROR. Mostly the sensor must have failed before replacing it just confirm the connection to the sensor are tight enough and if they are intact and still the error arises then replace the sensor.
You can buy the sensor from the below link http://www.repairclinic.com/PartDetail/Sensor/6501FA2462C/1268235