Diagnosis
The sanitize indicator illuminates only when the final rinse water reaches 162°F. Failure to light indicates the water did not reach that temperature.
How to Fix It
Ensure you are using a cycle that includes sanitize, like Auto, Heavy, or Sanitize. Check your home's water heater setting. It must be set to at least 120°F to allow the dishwasher's booster heater to reach 162°F. Run a hot water tap near the dishwasher before starting a cycle to clear cool water from the line.
If That Didn't Work
The internal booster heater or its temperature sensor may be faulty. A diagnostic test cycle can check heater function, but this requires a specific button sequence detailed in the technical documentation.
Heads Up
Using the Eco or Rinse Only cycles will not activate the sanitize function, regardless of water temperature. The light is designed not to illuminate on those cycles.