Dear All,
I have Toyota 7FD30 and i have serious problem with my lifting and control valve, when i lift the mast, after a period of time it will go down slowly by itself, it's like the control valve can't hold the mast for long. I have checked all the seals and hose and it's dry no leaking all, i have replaced sealkit set (o-rings)in the control valve and it's not leaking and i have cheked the piston in control valve and it's in a good condition.
It really confusing, can anyone help? Thank you all.

And i have the error codes: 54,61,62,67,71. I have read the information for err codes 54,61,67 from this forum. For err codes: 62 and 71 anyone have clues? Thanks..