Patent 7136741 was granted and assigned to Hitachi (Japanese train) on November, 2006 by the United States Patent and Trademark Office.
When an operation of internal combustion engine is stopped, the power consumption of a control unit is lowered, to measure an elapsed time. When the elapsed time reaches a standby time, the processing of lowering the power consumption is cancelled, to diagnose whether or not the leakage occurs in an evaporation purge line of a fuel vapor processing apparatus.