Not new but when you’re black tank is empty and it is showing ont the gauges that it is full or partly full, as they say it needs flushing to clear the sensors
Found the best thing to use is DAWN . A couple of travel days with nearly full tank and 1/2 cup of dawn solved . Sensors now correct
Nice tip! For me, when tank flushing doesn’t clear a sensor, my method has been to dump a bag of ice down the toilet and drive around (or home) and problem solved. Thanks for sharing.