Hi Nicol, I had exactly the same problem with my freshly imported hybrid alphard. A yellow exclamation mark in a circle warning light appeared on the dashboard so I took it to a local garage and they were absolutely sure it's the worn break pads that need replacing. After they replaced them for £250 the warning was still there. So I plugged the car into a diagnostic app trhough the OBD2 port (I don't remember the exact error message) and did some googling and everything suggested that the problem is most likely the break capacitorm, which is exactly in the place behind the little grill which @smurf posted. I found a used one on Ebay for about £20 so it was not much of a risk if it wasn't it. And it did the trick! After replacing it, the warning light disappeared and it never came up again. The only problem was that the place where it is mounted is a bit awkward to access.
Good luck with it!