2006 Toyota LandCruiser 200 Series lost power towing uphill

If the engine power has returned since this episode, I’d be willing to suggest that what happened is that the vehicle had gone into limp-home mode. This happens when something like the transmission or engine becomes hot enough that to continue at normal pace might cause damage to the vehicle. It’s the car’s way of saving its own life, if you like. When it does, you can expect a warning light and a reduction in power, just as you experienced.

Towing a caravan up hills is a great way to get a transmission really hot, or even a turbocharged engine such as the one in your LandCruiser. If the vehicle returned to normal once it had cooled down, then you shouldn’t have any ongoing problems, but another oil change and perhaps transmission service might be a good idea as these fluids can lose their mojo once they’ve been really hot even once.