Toyota Repair: Automatic transmission

Question
I have a 2011 Toyota Fortuner 3d 4X4 auto.

I did some mods to the suspension and put larger tyres on.  I find now that we off roading the ATF light comes ons.  WIll it  help if I add another ATF cooler or a larger one?

Or should I just not drive in 4HL?

Answer
There is no reason to not use 4x4L or H or not drive off-road, be sure the transmission and transfer case have the correct fluid and the level is correct especially if the fluids were already changed and even if not the fluid levels should be checked, it may have a "sealed" transmission that uses the WS type ATF but the fluid can still be checked by using the factory recommended procedure since it most likely has no dipstick to check. If temperatures in your region and area where the truck is operated are a concern then an additional transmission cooler would be a good idea.