VW/Audi ECU Up for sale is a Working, in excellent condition Audi 4000 ECU. My list shows this fits many early 4000 5000 & even VW Scirocco models. VW/Audi part number 035 906 263   035906263  , Bosch part # 0 280 800 009   0280800009 . This is a very hard to find ECU due to the age of the car. This is the Lambda controller, A defective unit can cause a whole host of problems relating to lean or rich fuel mixture, which can cause excess smoke, poor gas mileage, no start condition, no start when hot, no start when cold, or overheating caused by lean running. These units are not getting any easier to find, and it's always a good idea to carry an extra unit if you still run one of these cars.