Scyllas Grove. 4/4
1. Towards the bottom of the map you will see a vehicle location. On the map, directly above this you will a small dead end that goes the left. The symbol is in this dead end on the wall.
2. The area in from of the beginning of the level with the stairs leading up and all the little houses there will be an elevator at the very top. Once you get to the elevator back track just a small bit and you will see it on the side of the last building.
3. Looking at the map there is a dead on the far right side(below the vehicle station). As you walk into this dead end there is a 3 level building in front of you and slightly left. The symbol is on the left side of this building on the bottom floor.
4. Where claptrap is. At the top of the elevator go back to the far left corner(stay on the balcony'ish walkway). There are 3 ammo buckets in one corner of the balcony and three square crates in the other corner. Turn around and look at the door on the building and it's right above the door on a small overhang. (credit to the post below, didn't see what your name was, sorry lol)
Ardorton Station. 4/4
1. What looks like the middle of the map(still exploring) you will come across a room named "The Psycho Surgery". It has two small glowing blue plants in it. If you look outside the door you will see concrete stairs with another glowing blue plant at the top. To the right of these stairs is a two level building. On the bottom level is an enemy door, directly above this is a small room you can jump into and the symbol is on the ceiling.
2. Looking at the map from the beginning of the area notice the big circle. To the right of the circle is an area that you have to make your way around to called "The Ardo Farm". If you hug the bottom boundary of the map(heading towards the big circle) you will see a small ammo/money chest with a tiny wall behind it. Behind this wall is the symbol. (If your doing the DNA mission there is one in this area also).
3. From the beginning, once you enter the warehouse( "Bone Metal Camp" ), go through the other side which will be a dead end and also have a bunch of skags there. If you look straight ahead there will be a few spikes and one has a torch, the symbol is right there.
4. Once you get to the "Creature Lab" you will have to shut the lab down by hitting a switch. Before hitting the switch in the back corner of the room is a staircase that leads down. It's on the wall as you walk down near a weapons chest.
Candlerakks Crag. 3/3
1. During the mission "Big Feet" you will fight a boss named "Rogue". This area is the bottom of the map(keep going up as you travel to get there). The symbol is on a wall plain as day to the right if you walk towards the waterfall in the back corner. (On the map it's dead center on the bottom of that area).
2. After crossing the rope bridge on the way to the ship turn left. Once you get to the corner and have to turn right around the corner there is a house on that corner and the symbol is on the back of it.
3. Looking at the map, in the small area directly to the left of the "New You Station". This area is basically a huge circle with a bunch of scorpions in it and a huge pillar in the middle. The symbol is on the back side of the pillar. (credit mr01 - The third and final vault symbol is on a rock pillar near the split off on where you basically choose the left path to go to Voracidous and the right path to continue toward the ship (its the thickest rock pillar on the right path))
H.S.S. Terminus. 1/1
1. After killing the professor, as soon as you enter the room with the teleport, look up.