Happened to me at work twice now, thought I should give the warning. First time I thought it was a fluke, second time I noticed a pattern.
When you squeeze out the back window, the water will run PERFECTLY down the drivers side, down the inner quarter and funnel over a wiring harness that's part of the blindspot monitoring system, triggering a fault on the dash and saying see the dealer. Thankfully I work for a Honda dealership, so no biggie.
If in the event this happens to you- pop the trunk, pull back the trunk liner on the left hand side by removing the cargo hook tucked in the corner (pressure clipped in) and peel it back. The harness is right there when you pull it back, you can't miss it. Unplug both harnesses and take compressed air and blow all the water out and you're back in business. Won't throw a hard code, no need to go to the dealer if it happens.
Figured I'd save everyone the panic attack.