Display shows E16; the solution tank icon flashes even when the tank is full.

Safety: Disconnect power before removing tanks.

• Reseat tank: Remove the clean solution tank and reinstall it firmly until it clicks or seats fully. Ensure no debris is preventing full engagement.
• Inspect tank magnet/flag: Many Stihl tanks use a small magnet or plastic flag to trigger a reed switch or optical sensor. Check that this piece is not broken or missing.
• Check level float: If the tank has an internal float, verify it moves freely and is not stuck at the empty position.
• Sensor check: Locate the tank sensor on the main body and clean any detergent residue from its surface. Reseat its connector on the control board.