Fuel system diagnosis

The diagnosis of the fuel system checks the output values of the fuel trim adaptation described before. Above a temperature limit the adaptation of the integrator rkat or frau or frao are enabled depending on the operating area (see Figure). All integrator output values are compared to their calibrated upper and lower limits. If the integrator output reaches one of the limits after the adaptation has stabilized, a malfunction is detected, the engine conditions are stored and a corresponding fault is set. To avoid misdetections, the result of the diagnosis is delayed when the car is running out of fuel. For this purpose, a specific function for a near empty fuel tank is performed.