Automatic gear problem

Transmission oil pump or the torque converter may be faulty. a transmission specialist with the correct testing equipment can pin point the cause of this problem. there is no way of making a firm diagnosis with out testing first with the correct equipment. check around and see if your local transmission specialist can test this model, otherwise you will have to go see a dealer.

Thanks for your attention
the tests show poor pressure in the transmission fluid. But the tests do not show whether it is the actual real pressure inside transmission or pressure measured through sensors. Which means that we do not know whether the imbalance in the real pressure or in sensors and valves

That's where a line pressure test will help give you the info you need, a trans work shop can do this test fairly quickly and i should not cost very much to do,

Since here maintenance workshops do not know a line pressure test, please provide a detailed explanation and clarification
And please how to diagnose& repair non-shifting to 4th gear although 1&2&3 are fine

the line pressure is tested at the out let to the oil cooler or there will be a pressure point tap in with a screw in plug. You may have to get a live data read with a scanner, you may a faulty shift solenoid. I do not have a lot of technical data on this transmission, do you have a dealer in your town?