TOYOTA CAMRY 1999 Service Repair Manual

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 3 of 14
ORVR Operation
During refueling, low pressure above the
diaphragm in the onboard recovery valve
lifts allowing fuel vapors into the charcoal
canister. At the same time, the air drain
valve opens and the charcoal absorbs the
fuel vapors (see Figure 2).
Early Type (Non±Intrusive) EVAP System DTCs
EVAP Monitor Leak Operation P0440
The ECM tests for leaks by measuring
EVAP system pressure in the lines,
charcoal canister, and fuel tank. When
the EVAP pressure is higher or lower than
atmospheric pressure, the ECM
concludes that no leaks are present.
EVAP pressure is measured by the vapor
pressure sensor. If either the tank or
canister purge side is at atmospheric
pressure under specific conditions, the
ECM determines there is a leak.
If DTC P0440 is present, the leak is on
the fuel tank side of the EVAP system.
This also includes the lines between the
fuel tank and part of the canister. When
the Vapor Pressure sensor is measuring
tank pressure, the ECM is observing
changes in pressure and comparing tank
pressure to atmospheric pressure. No
difference in pressure indicates a leak.
The ECM may take 20 minutes or more to
complete testing the fuel tank side (see
Figure 3).
Canister Leak Detection P0446
When the ECM switches the vapor
pressure VSV to canister side, the ECM
measures canister pressure. A leak on
the canister side can set multiple DTCs
(see Figure 4).Early Type
System
Description
(Continued)
Figure 2. ORVR Operation
Figure 3. Fuel Tank Side of System
Figure 4. Canister Side of System

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 4 of 14
Vapor Purge Flow P0441
The EVAP monitor is designed to detect:
Restricted vapor purge flow when the
purge VSV is open
Inappropriate vapor purge flow when
the purge VSV is closed
Under normal purge conditions, pressure
pulsations generated by the cycling of the
purge VSV are present in the canister
and detected by the Vapor Pressure
sensor.
Three±Way VSV P0446
The three±way VSV is connected to the Vapor Pressure sensor, canister, and fuel tank.
This VSV allows the Vapor Pressure sensor to detect either canister or tank pressure.
There are two modes the ECM can use to determine if the three±way VSV is
malfunctioning. The three±way VSV is judged to be normal if there is pressure difference
between the tank and canister when the three±way VSV is switched to look at the
charcoal canister and fuel tank side of system.
If there isn't any pressure difference between the fuel tank and canister, the ECM looks
for the following conditions:
During purging, pressure pulsations generated by the purge VSV are not present in
the canister as detected by Vapor Pressure sensor, the three±way VSV is judged to
be defective.
If there are pressure pulsations detected by the Vapor Pressure sensor present in the
fuel tank, the three±way VSV is judged to be defective.
Late Type (Intrusive) EVAP System Overview
The Late Type EVAP System, also known as the Intrusive type, was developed to meet
the very stringent, mandated standard of detecting a hole 0.020 inch (0.5 mm). This
system uses many of the same components as the early type EVAP system. Purge,
vacuum relief, pressure relief, and ORVR operations are identical to the early type. Refer
to the Applicable Vehicles chart for applicability information.
The following changes were made to the Late Type EVAP System:
Vapor pressure sensor connected to the fuel tank.
Bypass VSV in the place of the three way VSV.
Canister Closed Valve (CCV) on the air inlet line.Early Type
System
Description
(Continued)
Figure 5. Flow During Purge Operation
Late Type
System
Description

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 5 of 14
Late Type (Intrusive EVAP System) (Except ECHO)
Onboard Recovery Valve
(Fill Check Valve)Vapor
Pressure
SensorVacuum
Check
ValveTank Valve
AssemblyTank
Pressure
Valve
Canister
To
Manifold
Vacuum
Purge
VSV
Filtered
Air
Air Drain Valve
Air Valve AssemblyAir Inlet ValveCanister
Closed Valve
Bypass
VSVAir
Inlet LineService
Port
Tank Side
The bypass VSV and the fill check valve
assembly isolates the tank pressure side
from the canister side (see Figure 1).
Canister Side
The bypass VSV and the Fill Check valve
also isolate the canister side from the
tank side (see Figure 2).
Late Type
System
Description
(Continued)
Except ECHO
Figure 1. Fuel Tank Side of System
Except ECHO
Figure 2. Canister Side of System

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 6 of 14
ECHO Late Type (Intrusive EVAP System)
The ECHO uses a Late Type EVAP System but is configured with some small
differences. For the ECHO, the Canister Closed Valve is located directly on the canister.
Additionally, the bypass VSV has been eliminated.
Onboard Recovery
Valve (Fill Check Valve)Vapor
Pressure
Sensor
Air Inlet ValveCanister
Canister Closed ValveAir Valve AssemblyAir Drain Valve Assembly
To
Manifold
Vacuum
Purge
Valve
Filtered
Air
Late Type (Intrusive) EVAP System Monitor Sequence
The monitoring sequence for leak detection is different from that of the Early Type EVAP
System. The Late Type applies a very small vacuum to the EVAP system. The ECM then
determines if there is a problem in the system based on the vapor pressure sensor
signal.
Monitor Sequence (Except ECHO)
CCV Open
Purge ClosedOpenClosed
Purge ClosedOpenOpen
Cold Start ECT/IAT
Near Same TempNegative
Pressure
(Vacuum)
OccursLeak Testing
Period OccursCCV
Op Open
Time in Minutes Bypass Closed
Closed
Bypass
VSV Op Vapor
Pressure
Sensor
Signal
P0441P0440
P0442P0446
Late Type
System
Description
(Continued)
Late Type
System
Monitor
Sequence

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 7 of 14
ECHO Monitor Sequence
CCV Open
Purge
ClosedOpenClosed
Purge ClosedOpen Open
Cold Start ECT/IAT
Near Same TempNegative
Pressure
(Vacuum)
OccursTank &
Canister
Leak CheckCCV
Testing Vapor
Pressure
Sensor
Signal
Monitor Operation
The monitor sequence begins with a cold
engine start. The IAT and ECT sensors
must have approximately the same
temperature reading.
The ECM is constantly monitoring fuel
tank pressure. As the temperature of the
fuel increases, pressure slowly rises.
The ECM will purge the charcoal canister
at the appropriate time (see Figure 1).
With bypass VSV closed, pressure will
continue to rise in fuel tank.
Late Type
System
Monitor
Sequence
(Continued)
Except ECHO
Figure 1. Canister Purge
ECHO
Figure 1. Canister Purge

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

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 9 of 14
Vent Control, CCV Operation P0446
This stage checks the CCV and vent (air
inlet side) operation. When the vapor
pressure rises to a specified point, the
ECM opens the CCV. Pressure will
increase rapidly because of the air
allowed into the system. No increase or
an increase below specified rate of
pressure increase indicates a restriction
on the air inlet side (see Figure 4).
Bypass VSV Operation P0446
In the next stage, the ECM closes the
bypass VSV. This action blocks air
entering the tank side of the system. The
pressure rise on the fuel tank side is no
longer as great. If there was no change in
pressure, the ECM will conclude the
bypass VSV did not close (see Figure 5).Late Type
System
Monitor
Sequence
(Continued)Except ECHO
Figure 4. CCV Opens
ECHO
Figure 4. CCV Opens
Except ECHO
Figure 5. Bypass VSV Closes

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 10 of 14
This diagnostic process tests the EVAP System. The following diagnostic tips may be
used in conjunction with the Diagnostic Procedures for EVAP DTCs listed in the Repair
Manual. They may be used for all Late Type (Intrusive) EVAP Systems and for all EVAP
DTCs. Refer to the Applicable Vehicles chart for applicability information.
The EVAP System Pressure Test Kit (P/N 00002±6872A) and the Scan Tool can be used
to diagnose the EVAP System. Measuring EVAP System pressures using the EVAP
System Pressure Tester Gauge and the Scan Tool can aid in the identification of leaks in
the system.
System Outline (Except ECHO)
Onboard Recovery Valve
(Fill Check Valve)Vapor
Pressure
SensorVacuum
Check
ValveTank Valve
AssemblyTank
Pressure
Valve
Canister
To
Manifold
Vacuum
Purge
VSV
Filtered
Air
Air Drain Valve
Air Valve AssemblyAir Inlet ValveCanister
Closed Valve
Bypass
VSVAir
Inlet LineService
Port
ECHO System Outline
Onboard Recovery Valve
(Fill Check Valve)
To
Manifold
Vacuum
Filtered
AirPurge
VSV
Air Drain
Valve
Air Valve
Assembly
Canister
Closed
Valve
Canister
Vapor
Pressure
Sensor
Air Inlet Valve
Air
Inlet LineService
Port
Diagnostic
Tips for Late
Type EVAP
System

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 11 of 14
Diagnostic Process Flow Chart
(Continued on following page)
PRELIMINARY CHECK
Fuel level should be between
1/4 and 3/4
Visually inspect for presence
of Fuel/Gas Cap
DO NOT TIGHTEN OR REMOVE!
PRESSURIZE EVAP SYSTEM (System Integrity Check)
This test checks for leaks in the canister and fuel tank sides. The CCV and Air Inlet Lines will be checked
separately.
A) Clamp the air drain hose on the charcoal canister with the supplied hose pliers from the EVAP System
Pressure Test Kit.
B) Locate the vapor pressure sensor. If the vapor pressure sensor has two hoses connected to it,
disconnect the hose between the air drain hose fitting at the vapor pressure sensor and plug the hose.
C) Connect the pressure supply hose from the Pressure Test Kit to the Green EVAP System Service Port
located on the EVAP Purge VSV line in the engine compartment.
D) Using the directions on the inside of the EVAP System Pressure Test Kit lid, pressurize the EVAP
system. Once pressurized, turn off the pump and seal the system (Pressure Hold Switch to ªClosedº
and Vent Switch to ªClosed).
E) After 30 seconds, note the pump pressure gauge reading and the Scan Tool vapor pressure
sensor reading.
F) Compare the readings to one of the four conditions listed below and proceed as directed.
DO NOT PROCEED! NG
OK
SCAN TOOL SETUP
A) Connect Scan Tool to DLC3 on vehicle.
B) Go to the SETUP menu and select UNIT CONVERSION.
C) Under VAPOR PRESSURE, Select ABS for absolute pressure, and mmHg for millimeters of mercury.
This is to match the Repair Manual specifications.
D) Go back to FUNCTION SELECT menu and select ENHANCED OBD II.
E) Select NORMAL MODE. Then select CURRENT DATA and USER SELECT.
F) Using the arrow key, select VAPOR PRESS from the DATA LIST and select YES.
G) Press ENTER. You will now be able to monitor the Vapor Pressure Sensor reading.
START
If vehicle is ECHO, go directly to ªECHO Canister and Tank Leak Checkº on page 14.
If vehicle is not ECHO, follow the flow chart below.
Diagnostic
Tips for Late
Type EVAP
System
(Continued)

EVAP SYSTEM OPERATION INFORMATION ± EG005-01 April 27, 2001
Page 12 of 14
Pump pressure
gauge and vapor
pressure above
atmospheric
pressure (above 762
mmHg). No leak in
canister or tank.Pump pressure
gauge zero, vapor
pressure above
atmospheric
pressure (above 762
mmHg). Leak is on
canister side of
system.Pump pressure
gauge is above
atmospheric
pressure (above
zero), vapor
pressure is at
762 mmHg. Leak is
on the fuel tank side
of system.Pump pressure
gauge at zero,
vapor pressure is
at 762 mmHg. The
leak(s) is/are on the
canister and tank
sides or a leak at a
point common to
both sides of system.
Remove hose pliers
from the air drain
hose on the charcoal
canister before
proceeding with
additional checks.Remove hose pliers
from the air drain
hose on the charcoal
canister before
proceeding with
additional checks.Remove hose pliers
from the air drain
hose on the charcoal
canister before
proceeding with
additional checks.
Go to CCV/Air Inlet
Line Check.Go to ªCanister Leak
Check.º Diagram on
page 13.Go to ªFuel Tank
Leak Check.º
Diagram on page 13.Go to ªFuel Tank
Leak Check.º
Diagram on page 13.
Remove hose pliers
from the air drain
hose on the charcoal
canister before
proceeding with
additional checks.
Go to ªReturn Vehicle to Serviceº on page 14.
CCV and Air Inlet Line Check. (Except ECHO)
A) Disconnect the air inlet line from the charcoal canister.
B) Using the supplied step±down brass adapter (or equivalent) connect the Pressure Supply Hose to
the air inlet line.
C) Using the Scan Tool Active Test, turn on the CCV. This will close the CCV.
D) Pressurize the line. Once pressurized, turn off the pump and seal the line (Pressure Hold Switch to
ªClosedº and Vent Switch to ªClosedº). Pressure should hold. If not, check CCV and connections.
E) Next, using the Scan Tool, turn off the CCV. This will open the CCV. The pressure should decrease.
If not, check the CCV and connections.
F) After completing the test, reconnect air inlet line to charcoal canister. Diagnostic Process Flow Chart (Continued)
(Continued from previous page)
Diagnostic
Tips for Late
Type EVAP
System
(Continued)