A car's wiring harness is a miles-long series of wires and connectors that brings the whole vehicle together, electronically speaking. When one part isn't plugged in, your car's computer isn't receiving all the information it possibly can, which is the reason for Toyota's latest recall.
Toyota issued a recall covering just 7,100 examples of the 2016 Toyota Highlander crossover. The issue relates to the car's massive wiring harness. The portion of the harness that connects to the brake fluid reservoir sensor might not be plugged in, which means that a warning light may not illuminate, which places the Highlander in violation of federal safety standards.
Brake fluid is used to transfer pressure from your right foot to the vehicle's individual brake calipers. If the fluid level is low, the brakes may not perform as intended, raising the risk of a crash. Usually, there's a warning light that pops up when the brake fluid gets low, but without that wiring harness connector in place, there won't be a warning light at all.
Toyota will notify the thankfully small number of affected owners in early November. To remedy the issue, dealerships will inspect the brake fluid reservoir and, if necessary, plug in the wiring harness correctly. Hell, if you know what to look for, you could probably do it yourself.