Sulfur in fuel interacts with certain additives found in widely available gasoline causing sulfur to become deposited on the contact points of three fuel sending units mounted inside the fuel tank. This could cause the fuel gauge to read full while the fuel tank may not in fact be full or could be empty.

Running out of fuel without warning while the fuel gauge indicates that there is sufficient fuel in the tank lead to safety problems.

Dealers will remove the existing fuel level sending units and replace them with fuel level sending units using a new alloy composed of gold, silver, and a small amount of nickel, which will not chemically react with sulfur. (VW/Audi will also call back vehicles that were repaired under a previous recall last June in order to install the updated fuel sending units NHTSA 00v137/Audi label.