If after washing it, you get a "water in fuel" WIF light, don't panic just clean the WIF sensor connector and apply some dielectric grease to it. Also try not to hit any of the wiring with a high pressure stream of water, it can cause a lot of damage to brittle under hood plastic anything. Any auto cleaner will work; Castrol Super Clean or even Armour All Cleaner, just make sure it is for cars.
High pressure water and radiators don't mix, unless you want a lot of bent fins.