A vapor management system (10) includes a fuel tank (12), a canister (14), a pressure control valve (16) between the tank and canister and defining a high pressure side (34) and a low pressure side (32), a vacuum source (18), a purge valve (19) between the canister and vacuum source, a leak detection valve (20) connected with the canister and including a processor (30). A pressure sensor (24) and a temperature sensor (26) are disposed in a fuel vapor cavity of the fuel tank, with signals from the sensors being received by the processor. Based on an absolute temperature measured by the temperature sensor, the processor compares a predicted pressure in the fuel tank to the measured absolute pressure, and identifies a leak on the high pressure side if the predicted pressure is outside a tolerance range, while maintaining pressure in the fuel tank.