I have a 1995 4-Runner that we put a used transmission into because the old trans kept overheating. After I put the new one in, I could drive about 40 miles and the light would come back on. The local dealership told me to put in a new radiator, so I did. Still does it. I installed a large aftermarket trans cooler. The light still comes on. Anyone know what causes this??

 

spoke to a Toyota tech about this. He mentions that it could be due to too much trans fluid in there. This could be a bad thing as too much could cuase foaming and then hot spots. Try checking your fluid level.