A failure diagnosis method and a failure diagnosis system of a dual purge system may determine whether a closed stuck failure or an opened stuck failure occurs in a line forming a dual purge system by measuring a pressure in a negative pressure formation device and comparing the corresponding pressure with a predetermined reference value when a purge valve of the dual purge system is in an opened or closed state, and may determine whether the failure occurs in components related to a secondary purge line in the dual purge system in which it is difficult to determine whether the failure occurs in a conventional failure diagnosis method of a single purge system in a simple method.

Methods and systems are provided for an evaporative emissions control system for onboard refueling vapor recovery of a heavy duty vehicle. In one example, a method may include, in response to greater than a threshold change in a fuel level of a fuel tank fluidically coupled to at least two fuel vapor storage canisters of an evaporative emissions control system during a refueling event, performing a canister working capacity diagnostic on each of the at least two fuel vapor storage canisters by measuring an exhaust gas air-fuel ratio (AFR) while independently purging each of the at least two fuel vapor storage canisters. In this way, the working capacity of each fuel vapor storage canister may be separately assessed in order to more accurate identify degradation of the working capacity.

A fuel vapor treatment apparatus includes a controller configured to detect an abnormality in at least one of a first check valve, a second check valve, a second purge passage, a charging passage, and an ejector based on pressure detected by a pressure detector.

A method for performing an on-board diagnostic function in a motor vehicle including at least one drive system, at least one operating element and at least one control unit with a processor, a control module and an on-board diagnostic function module. The method includes the steps of: activating an on-board diagnostic function in the on-board diagnostic function module; supplying a first signal profile (S1) of an operating value (CV) of the operating element to an analysis module; the analysis module analyzing the first signal profile (S1) of the operating value (CV); activating a filtering module in the event of a positive analysis result; and the filtering module filtering the first signal profile (S1) of the operating value (CV) with selected damping parameters (DP) upon activation of the filtering module in order to obtain a filtered second signal profile (S2) of the operating element.

A fuel tank system for a vehicle includes a fuel tank, a fuel supply passage, a canister, an evaporated fuel gas supply passage, a communication passage, a backflow prevention device, first and second pressure measurement devices, and a control device. The fuel tank stores fuel supplied by the fuel supply passage. The canister adsorbs evaporated fuel gas generated in the fuel tank and supplied through the evaporated fuel gas supply passage. The backflow prevention device is provided in a pipe line of the fuel supply passage, and prevents a backflow of the fuel from the fuel tank. The first and second pressure measurement devices respectively measure pressures in the fuel supply passage and the evaporated fuel gas supply passage. The control device diagnoses the communication passage as being blocked when a difference between pressure values measured by the first and second pressure measurement devices exceeds a predetermined value.

Methods and systems are presented for operating a refueling valve of an evaporative emissions system. The methods and systems may attempt to reactivate a refueling valve that has stuck due to the refueling valve being exposed to liquid fuel. In one example, a voltage that is applied to the refueling valve may be increased to reactivate the refueling valve.

A method for diagnosing fuel leakage of a vehicle includes: measuring a pressure of a fuel tank by a pressure sensor in a closed state of a fuel system during starting-off of the vehicle; measuring an inner temperature of the fuel tank by a temperature sensor; and diagnosing, by a controller, whether or not leakage occurs by performing different leakage diagnoses depending on a pressure condition of the fuel tank. Thus, the controller performs a first leakage diagnosis when a pressure value of the fuel tank, measured in the measuring the pressure of the fuel tank, is within an atmospheric pressure level; performs a second leakage diagnosis when the pressure value is higher than a positive pressure; and performs a third leakage diagnosis when the pressure value is lower than a negative pressure.

Methods and systems are provided for diagnosing potential degradation of a fuel tank pressure sensor. In one example, a method may include, in response to an ambient pressure reading by the fuel tank pressure sensor during an evaporative emissions (EVAP) system diagnostic, applying vacuum to the EVAP system and indicating degradation of the fuel tank pressure sensor if the canister undergoes an endothermic reaction. If the fuel tank pressure sensor is determined to not be degraded, the method further includes distinguishing between the ambient pressure reading being caused by a leak in the EVAP system and a canister purge valve being stuck closed.

A fault diagnosis method is provided for an evaporated fuel processing device including a canister including a charge port connected to an upper space of a fuel tank, a purge passage connecting a purge port of the canister and an intake system, and including a purge control valve, a drain passage including a drain cut valve, and a pressure sensor. The pressure sensor is configured to sense, as a purge passage pressure, a pressure between the purge control valve and the canister in the purge passage. The fault diagnosis method includes performing a purge by opening the purge control valve in a state in which the drain cut valve is controlled to be opened; measuring an actual pressure variation by the pressure sensor; and diagnosing a closing fixation of the drain cut valve by comparing a predetermined pressure variation and the actual pressure variation.

Methods and systems are provided for reducing a possibility of hydrocarbon (HC) breakthrough during a diagnostic routine of an evaporative emissions control (EVAP) system. In one example, a method may include, during the diagnostic routine, switching a direction of air-flow through a fuel vapor canister via adjustments to a three-way valve in response to a higher than threshold a change in temperature within the canister.