The Digifant system is all electronic, using electric injectors at a low injection pressure. All injectors are operated by the Electronic Control Unit (ECU) so injector timing and duration can be closely controlled for reduced emissions and improved fuel mileage. During deceleration above a specific rpm, the injectors are shut off to save fuel and reduce emissions. The air flow sensor uses an air vane that moves a potentiometer to signal its position to the ECU. The electric idle stabilizer a motorized rotary valve that controls the amount of air allowed to bypass the throttle plate. Very precise control is maintained over a wide range of idle loads and engine temperatures. The ECU has the ability to store fault codes but codes and other self diagnostic functions can only be read with the VAG 1551 tester. Procedures described here are for testing without the VAG 1551.