After you are done with the AT-TE walker part on Kashyyyk which unlocks after you are done with Tomb Of Eliram on Zeffo, you will meet Saw Gerrera. In your process to locate Tarfful on Kashyyyk you will unlock BD-1’s upgrade called as Overcharge Ability. With this ability BD-1 can now turn on and off machinery, a highly helpful ability in coming levels. Here what you have to do to unlock this upgrade.
How to unlock Overcharge Ability for BD-1 Walkthrough
There is an entrance to the trench towards the right end, just cross the big metal door. Go to the right, yo cannot move ahead until you unlock the ability. Just on the right of door there is an path covered with pipes cut them and you will see a Workbench.
This place is guarded by a huge spider. It is a tough enemy and keep a few health stims ready with you. You have to evade the spiders web attack, press circle to break if you are caught. Use a lot of evade and roll to avoid the attach and whenever you have chance hit from the back.
The spider can also dash in with full speed that can flip you over, it will take a little time to take down this creature. You can also try to to deflect the web back on the spider, but I am not sure whether it works give it a try.
After defeating it interact with the work bench in the room corner and you will unlock the new Overcharge Ability that will help BD-1 to turn on and off machinery. Return back to the trench and use the new ability to move the huge metal platform for wall run to move forward.