Patent ID: 8630786

Claim:
A vehicle comprising: an internal combustion engine; a sealed fuel system having a fuel tank, a canister for storing fuel vapor from the fuel tank, a vapor circuit positioned external to the fuel tank and in fluid communication with the fuel tank, and a control valve for controlling a flow of fuel vapor from the vapor circuit into the canister, wherein the vapor circuit includes an absolute pressure sensor, a pump, and a switching valve selectively connecting the fuel tank to the absolute pressure sensor when the control valve is open; and a controller having an algorithm, the execution of which by the controller causes the controller to diagnose a vapor purge function of the sealed fuel system using vacuum measurements from the absolute pressure sensor; wherein the controller is configured to execute the algorithm only when the engine is running, vapor purge is enabled, and the pump is off, and diagnoses the vapor purge function while the pump remains off by comparing the vacuum measurements to a calibrated vacuum.