Matt, Im in Lagos Nigeria and have a rav4 2001 with brainbox issues. When I bought the car the initial brainbox which came with the car was changed. The car would not start and i was told the demobiliser was faulty. Bought another brain box ( this was about 4 years ago) and now the car doesnot change gears smoothly it jerks, is slow changing from gear one to two and then jerks into higher gears. Just need to know how to solve problens but found out that would have to pay 13 pounds if satisfied with answers. However it seems that this is a monthly fee???? I am willing to pay the 13 pounds if satisfied with answers from Matt. but just as a one off fee.
I'd take a look at the colour of the transmission oil it should be a dark red colour if its black then its needs changing together with its oil filter. Also check its level with the gearbox warm and just after you've moved the selector through all the positions leaving it for a few seconds in each one and then back to park.
You can top up the box through the side fill plug if required and make sure you use the correct oil for your car as the fluids are not all the same. Some manufacturers recommended a change of the type of fluid - Speak to the local dealer and parts dept - they will advise you on the updated fluid to use..
If that’s all OK then check all the electrical connections of the gearbox, remove each connector in turn and spray with contact cleaner. Check that the wiring to the gearbox is in good condition with no chafing or frayed wire
If this is OK then check the selector lever linkage / cable under the car for any broken parts and or missing bolts as if this is coming adrift then it can rub on the car body or just bind up
Then - you should top up if low and re try it - or, if its level is ok - and condition is ok - then the next step is to drain it off - open it up and clean the filters inside -- refill and retry it..
Thanks Matt, Can I come back to you in a couple of days with answers to your suggestions. For the record Im female and would need to let the local mechanic take a look and follow your instructions