Instructions on calibrating the fuel tank volume for a digital instrument cluster

The procedure for calibrating the fuel tank level system on '89+ cars is detailed in section 20-19 of the service manual.

Starting with an empty tank, add 15 liters (3.96 gallons) of fuel to the tank. Allow the sender to settle for a few minutes. Pull the
operating lever for the display unit, and turn the ignition on while holding the lever. The display will read "TANK EICHEN" (calibrate tank) in the left display, and "15 LITER" in the right display. Press the reset button in the center console until "15" appears in the center
display. The system is now calibrated. Use this procedure after the instrument cluster is removed or the tank sender is disconnected for any reason.