EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 8 of 14
Purge VSV Operation ± P0441
At a predetermined point, the ECM closes
the CCV and opens the bypass VSV
causing vacuum to increase in the entire
EVAP system.
The ECM continues to operate the purge
VSV until the vacuum is increased to a
specified point at which time the ECM
closes the purge VSV (see Figure 2).
If the vacuum did not increase, or if the
vacuum increased beyond the specified
limit, the ECM judges the purge VSV and
related components to be faulty.
Hole Detection P0440 and P0442
The rate of pressure increase as detected
by the vapor pressure signal indicates the
if there is a leak and if it is a large or
small leak.
After purge VSV operation, the purge
VSV is turned off sealing the vacuum in
the system and the ECM begins to
monitor the pressure increase (see Figure
3). Some increase is normal. A very rapid,
sharp increase in pressure indicates a
leak in the EVAP system and sets the
DTC P0440.
This monitoring method is also able to
distinguish what is called the small leak
detection. A pressure rise just above
normal indicates a very small hole and
will set the DTC P0442.Except ECHO
Figure 2. Vacuum Application
Late Type
System
Monitor
Sequence
(Continued)
ECHO
Figure 2. Vacuum Application
Except ECHO
Figure 3. System Sealed
ECHO
Figure 3. System Sealed
