A4 Documentary: Fuel Drop After Reserve (1999) (Solution)

The fuel gauge drops very quickly after reaching the reserve level.

Cause:
The wiring harness for the fuel consumption signal between the engine control unit and the instrument cluster was not installed at the factory.
Since the absence of this signal causes the control panel to indicate maximum consumption, the minimum value of 15,000 km is used in the calculation of the flexible maintenance interval. Additionally, the fuel gauge drops very quickly from the reserve level to "empty."

Solution:
Install cable number 8D0 971 068 between the blue T32 connector, chamber 25 on the distribution panel baseplate, and the coupling station T10, chamber 10 in the electrical box, into the water reservoir.
The cable should be run parallel to the existing wiring harness, stripped of its outer insulation, and secured with zip ties.