Celica Forums Thread Like Summary - Toyota Celica GTS 2000 - Erratic Shifting (automatic)

hi guys, please, help me, i don't know what else to do, i have a toyota celica gts 2000 auto trans,285,000 miles with erratic shifting problems.
it suddenly happen from the nothing, i was driving normal, like any other normal day, i always change the oils when it needs to, but suddenly it begins to have problem at the shifting moment, it became pretty slow since 1 gear until the 4th gear.

after that when i was 1st gear was great, 2nd gear too, but 3rd gear was putting my revolutions down and started to literally break, then check engine light turned on and it stopped the erratic shifting, but now, it doesn't use 4th gear, it is like if the 4th gear never existed, like if i were driving it without overdrive on, i already changed the transmission, but had the same problem, i already changed the TPS SENSOR, MAP sensor, knock sensor, checked every cable in the transmission and the whole car, but every thing looks to be okay, my only option left is the ECU, but i don't think that's the problem because, the computer is doing auto corrections, that's why it stopped shifting into 4th, and right now it is only working with 3 gears, i don't know what to do can anyone help me? please, i'm so frustrated

There may be debris that block the gear to shift to 4th gear.

You can try to flush the tranmission. Buy flushing fluid at Walmart or auto part shops. Follow instructions.

Jack up the front driving wheels, pour flushing fluid in mine, idle the engine, shift back and forth all 4 speeds to make sure all gears are flushed.

Then drain the fluid, add back in the 4 or 6 quarts of new fluid to fill the pan.

Remove the transmission fluid return line from the radiator to the xmission, stuck it into a large, clear can, like a gallon milk bottle.

Again idle engine while shifting through all 4 speed. Have someone keep adding fluid into the dip stick hole. Watch the flushed fluid in the bottle. After adding 4 to 6 quarts of fluid, the drained fluid should look clear, fresh and red. Then xmission is completely flushed. Hopefully the debris is flushed out and unstuck your 4th gear.