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When you get the Trans Check Light, - this means the TCM, Trans Control module , has detected a fault somewhere
in the transmission system.
This can be in the actual transmission itself - the electrics, wiring or even the TCM itself though the latter is quite rare.
BUt the first place to start is the transmission fluid. Check to see if it is at the correct level- and that it looks a nice red-ish colour. If its black and smells burned, thats a sign of internal transmission trouble which would then have to be investigated further. If its conditionis good but level low, top up and re try it.
If its nothing to do with the fluid, then the next step is to have a fault code read done.
When the light comes on as you describe, the trans sticks in 3rd gear. That is because the TCM invokes what is called limp or safe mode... and invokes 3rd gear use only... this is to protect the systems while the fault exists. The TCM will have fault codes relating to the fault - which as above, need to be read, and that will point to the fault so that it can be sorted / fixed whatever it is.
As you say, switching off / on again resets it.. thats normal. That will happen , until the next time.
So work through as above on this one to get this cured for you now.
I sincerely XXXXX XXXXX above all helps you and helps with the understanding of the problem you have -and what needs to be done to cure this ...
Kind Rgds, MIKE.
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