Monitor Description

The EVAP monitor's purpose is to check for EVAP leaks and EVAP VSV and CCV malfunctions. The monitor performs the check by first introducing the intake manifold's negative pressure (vacuum) to the EVAP system. Then, the monitor records change in the EVAP system's pressure levels. The monitor runs when the following conditions are met:

• The engine coolant and intake air temperatures are 4 to 35°C (40 to 90°F).
• The engine is idling or the vehicle is being driven at a steady speed.
• The fuel tank pressure is stabilized.

  LEV II EVAP Monitor Process

  Fig 1: Identifying LEV II EVAP Monitor Process

  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  OPERATION DESCRIPTION CHART
  
  

  Sequence	Operation	Description
  1	Fuel vapor measurement	EVAP VSV is turned OFF (closed) and EVAP pressure is measured. If EVAP pressure is not stable, EVAP monitor is canceled to prevent inaccurate monitor.
  2	Vacuum introduction	EVAP VSV is turned ON (open) and CCV is turned ON (closed). As a result, intake manifold pressure (vacuum) is introduced to EVAP system.
  3	EVAP leak check	EVAP VSV is turned OFF (closed) to seal EVAP system. EVAP pressure increase is measured for 5 seconds when EVAP pressure is - 20 mmHg and -17 mmHg. If increase is large, ECM concludes EVAP system has leak.
  4	Restore	CCV is turned OFF (open) to finish EVAP monitor.

LEV II EVAP Monitor Sequence

Fig 2: LEV II EVAP Monitor Sequence Chart

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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