Gearbox controller is one of the most important elements of an automatic gearbox as it controls the automatic transmission and ensures that it is steered with appropriate oil pressure. The functioning of an automatic gearbox depends to a large extent on this very controller, which, if it is defective, disrupts the whole functioning of the gearbox and causes a lot of irregularities, including stiff gear change (jerking) or too soft one (slippage). The defective gearbox controller also contributes to premature wear of other parts of the vehicle, such as the clutch or brake discs. So, in order to keep the car in good condition, action must be taken as soon as a defect appears. Occasionally, a defective controller can be repaired; however, in the majority of cases a replacement thereof is necessary.