This is how I fixed it:
My Rav4 had the classic issue with the gearbox. Banging into reverse, slipping between 1 and 2 andd then banging 2nd into place. High fuel consumption.
I identified the problem, the ECU needed resoldering of the resistors.
I took the unit away, opened it and added a tiny amount of solder on all the bigger compontents on both sides of the board. Power resistors, surface mount resistors, capacitors, diodes and transistors. I even resoldered the big connector. Be careful when you solder so you dont overheat the components, especially the diodes and transistors. Be quick on every solder joint and dont put too much new solder. You can also use only flux and reheat the soldering joint, but I had no flux so I needed to solder a little bit with flux containing solder. I used lead free solder and it worked fine. Use a cheap small tip soldering iron used for electronic components and clean the tip using a sponge between every few solderings.
This took away the initial problems, but now instead the gearbox slipped between 2nd and 3rd gear before banging it into place. I researched more and found out that the ECU has a self-learning function to know when to change the gear. The ECU have been learning how to shift with broken solder joints on the small resistors that is involved with shifting. After you solder the joints to the small surface mount resistors, the ECU:s self-learned memory needs to be cleared. Toyota can do this if you clearly describe the problem and they understand it, but it is way cheaper and easier to do it yourself.
I ordered a MINI-VCI cable for around 20-25 USD from Ebay that came with a small CD with the Toyota Techstream diagnosis application. I installed the applicationon my old Windows XP laptop, as it is made for older operating systems. I did not try on my newer laptop, but maybe it works if you can use the "run on Windows XP" in the right-click preferences menu.
I connected the cable to the computer and OBD socket, chose the right car and model. Select the ECU in the list (engine ECU) and press the green arrow. Wait until it loads and press Utilities (or similar). There you can choose to erase the memory for the self learning function.
Efter this I started the car and now it shifts like a dream again. Thanks everybody on this forum.
Well in case you didn't see my little post in that 20 page thread, I have a video posted which describes how to fix your rav4 ecu yourself. It takes about fifteen minutes and all you need to do is re-solder some resistors. I have verified that this is the problem, and that this is the proper fix to it. In the video description there are links to two still pics which highlight the resistors that need soldering.
Please leave comments about your successful repair so that others will know that the fix is genuine. Thanks-Jake