Cat 320B Hydro and electrical problems need help!!

The 320b can't read how fast the engine is running, it is reading 00 when I run service code 12 so i think that is causing my engine bogging/stalling problem. I have been trying to use the book to check codes and to try and run some tests to find the problem. I tried to shut the computer off by using the switch behind the right arm rest and the screen and the computer stay on so i can't see if it is a controller or electrical problem... I was using the book to try and figure out the RPM issue, i took out the speed sensor and cleaned it off and reset it back in possision according to the book but still no reading....The engine speed dial works and shows 1 thru 10 on the display but the engine wont start/stay running unless its set on number 4 and it runs like if its set on number 1, which is why i think its a speed problem because its set to 10 and the computer i think is thinking that its running at full RPM or it can't tell if the engine is bogging or not. I have been trying to follow the book with what it says on how to chase the problem but the way the book is worded i am having a bit of trouble knowing where each connection is and exactly how to test it...the book needs more pictures. Also i have hydro oil leaking out of the middle of the main hydro pump and the engine where the flywheel is and the engine speed sensor which is why i took out and cleaned off the speed sensor...since there is no drain plug there i had to drill a small hole on the bottom to let out some oil hoping that would help me out and to get any kind of number on the dash for the RPMs.... I know at some point i will have to change the pump and or have the seals replaced but for now i would like to get the other problems fixed and or working... The machine works for the most part and will stall if i don't let go of the controls at the last second to let the engine catch back up....

I have changed ALL of the filters, even the three for the hydro...

The action that most effects the bogging is the stick out, not so much boom up or curl or uncurl in or out or stick in but stick out like when you go to reach far away from the machine to get a scoop of dirt.... PLEASE HELP I AM AT MY WITS END!!!

sounds like you are on the right track. The speed sensing does indeed only matter in speed dial 10. If you run in speed dial 9 - the PRV pressure to the pumps is constant. It only varies to control HP load in dial 10. Check the speed pickup with an ohmmeter. Should read 110 to 280 ohms. And then, if you have a meter that reads AC voltage and frequency, with engine running should measure 1700Hz to 4700Hz coming out of the speed pickup and about 4 to 10 volts AC.
If all that checks out - start following those 2 wires to the controller on the floor of the cab.

Once you get that signal restored, you can go through the PRV and Governor Actuator calibrations.

I got 4 or a little more volts ac, I can't check Hz though...those two wires on the floor of the cab, are those the wires that run from the speed sensor to under cab by your feet if you were sitting in the cab?

I also don't know how to clear the fault codes, there are many faults and I don't know which ones are still active or old codes that are just saved in the computer

you view active codes on one service mode "channel" and logged codes on another "channel" so shouldn't be any confusion about what's which.

The main computer is beside the seat on the cab floor - behind operator's right heel. The machine schematic identifies all the pin-out's and wire function, colours/harness numbers at the ECM