My 2005 Journey has external proximity sensors on the gray water holding tank for detecting the waste water level. These are the black square stick on type with the white + sigh in the center. Like most other types of sensors they are susceptible to sending false positive signals when guck builds up on the inside of the tank. When Dish soap and tank cleaners don’t do the job, I have the good solution to the problem.

Cut off the female end of a flexible garden hose about 3-4 feet...