Physical damage to ECU is not covered under warranty in Pakistan. I don't know if Toyota in Canada covers that. Please check the warranty documents carefully before splashing the expensive ECU with water.
Toyota Indus puts a bilingual sticker in YELLOW COLOUR inside the hood, advising against washing the engine.
At Toyota dealerships, they don't wash the engine compartment. They just get rid of the dust through high pressure air.
I get Laadli's engine washed every month, after carefully covering the ECU in at least two layers of plastic bag. Now, that the ECU cover is there, no need to cover while washing
This is the ECU cover