Toyota Sequoia (2005). Manual — part 154
A23480
Fuel Tank
Canister
Vacuum Pump: OFF
Pressure Sensor
0.02 Inch Orifice
Pump Module
Operation A: Atmospheric Pressure Measurement
Vent Valve: OFF (vent)
Operation D: Purge VSV monitor
Operation B: 0.02 Inch Leak Pressure Measurement
Negative
Pressure
Atmospheric
Pressure
Operation C: EVAP Leak Check
Air Filter
Purge VSV: OFF
OFF (vent)
ON
OFF
OFF
ON
ON (closed)
ON
ON
ON (closed)
–
DIAGNOSTICS
ENGINE
DI–411
605
MONITOR DESCRIPTION
5 hours* after the ignition switch is turned OFF, the electric vacuum pump creates negative pressure (vacu-
um) in the EVAP (Evaporative Emission) system. The ECM monitors for leaks and actuator malfunctions
based on the EVAP pressure.
HINT:
*: If the engine coolant temperature is not below 35
C (95
F) 5 hours after the ignition switch is turned off,
the monitor check starts 2 hours later. If it is still not below 35
C (95
F) 7 hours after the ignition switch is
turned off, the monitor check starts 2.5 hours later.
Sequence
Operations
Descriptions
Duration
–
ECM activation
Activated by soak timer, 5 hours (7 or 9.5 hours) after ignition switch turned to OFF.
–
A
Atmospheric pressure
measurement
Vent valve turned OFF (vent) and EVAP system pressure measured by ECM in order to
register atmospheric pressure.
If EVAP pressure is not between 70 kPa and 110 kPa (525 mmHg and 825 mmHg), ECM
cancels EVAP system monitor.
10 seconds
B
First 0.02 inch leak
pressure measure-
ment
In order to determine 0.02 inch leak pressure standard, vacuum pump creates negative pres-
sure (vacuum) through 0.02 inch orifice and them ECM checks if vacuum pump and vent
valve operate normally.
60 seconds
C
EVAP system pres-
sure measurement
Vent valve turned ON (closed) to shut EVAP system.
Negative pressure (vacuum) created in EVAP system, and EVAP system pressure then
measured.
Write down the measured value as it will be used in the leak check.
If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor.
15 minutes*
D
Purge VSV monitor
Purge VSV opened and then EVAP system pressure measured by ECM.
Large increase indicates normal.
10 seconds
E
Second 0.02 inch leak
pressure measure-
ment
Leak check is performed after second 0.02 inch leak pressure standard is measured.
If stabilized system pressure higher than second 0.02 inch leak pressure standard, ECM
determines that EVAP system leaking.
60 seconds
F
Final check
Atmospheric pressure measured and then monitoring result recorded by ECM.
–
* If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.
A23664
Purge VSV
Vent Valve
Vacuum Pump
EVAP Pressure
Positive
Leak Pressure
sec
Negative
ON
ON
Sequence
Time
A
10
sec
60
Within 15 minutes
ON
First 0.02 inch
B
C
D
OK
Malfunction
ON: Open
OFF: Closed
OFF: Vent
ON: Closed
10
Standard
sec
60
E
sec
EVAP Pressure when Vacuum Pump Stuck OFF:
DI–412
–
DIAGNOSTICS
ENGINE
606
(a)
P2401: Vacuum pump stuck OFF
In operation B, the vacuum pump creates negative pressure (a vacuum) through the 0.02 inch orifice. The
EVAP (Evaporative Emission) system pressure is then measured by the ECM, using the pressure sensor,
to determine the 0.02 inch leak pressure standard. If the pressure is higher than –1.06 kPa (–7.95 mmHg)*,
or lower than –4.85 kPa (–36.38 mmHg)*, the ECM interprets this as the vacuum pump being stuck OFF
(not operating). The ECM illuminates the MIL and sets the DTC (2 trip detection logic).
*: The thresholds vary according to the atmospheric pressure measured in operation A. The values de-
scribed above are based on an atmospheric pressure of 100 kPa (750.1 mmHg): absolute pressure.
A23663
Purge VSV
Vent Valve
Vacuum Pump
EVAP Pressure
Positive
Leak Pressure
sec
Negative
ON
ON
Sequence
Time
A
10
sec
60
Within 15 minutes
ON
First 0.02 inch
B
C
D
OK
Malfunction
ON: Open
OFF: Closed
OFF: Vent
ON: Closed
10
Standard
sec
60
E
sec
EVAP Pressure when Vacuum Pump Stuck ON:
–
DIAGNOSTICS
ENGINE
DI–413
607
(b)
P2402: Vacuum pump stuck ON
In operation B, the vacuum pump creates negative pressure (a vacuum) through the 0.02 inch orifice. The
EVAP (Evaporative Emission) system pressure is then measured by the ECM, using the pressure sensor,
to determine the 0.02 inch leak pressure standard. If the pressure is higher than –1.06 kPa (–7.95 mmHg)*,
or lower than –4.85 kPa (–36.38 mmHg)*, the ECM interprets this as the vacuum pump being stuck ON (re-
maining ON all the time). The ECM illuminates the MIL and sets the DTC (2 trip detection logic).
*: The thresholds vary according to the atmospheric pressure measured in operation A. The values de-
scribed above are based on an atmospheric pressure of 100 kPa (750.1 mmHg): absolute pressure.
HINT:
The detection logic of DTCs P2401 and P2402 is the same because in both cases the 0.02 inch leak pressure
standard measured in operation B is compared to the atmospheric pressure registered in operation A. The
ECM calculates the difference between these pressures by deducting [the 0.02 inch leak pressure standard]
from [the stored atmospheric pressure], and uses this to monitor the EVAP system pressure change.
MONITOR STRATEGY
R l t d DTC
P2401
Vacuum pump stuck OFF
Related DTCs
P2402
Vacuum pump stuck ON
Required sensors/components
Pump module
Frequency of operation
Once per driving cycles
Duration
Within 2 min.
MIL operation
2 driving cycles
Sequence of operation
None
DI–414
–
DIAGNOSTICS
ENGINE
608
TYPICAL ENABLING CONDITIONS
It
Specification
Item
Minimum
Maximum
The monitor will run whenever these
DTCs are not present
See page
Following values are when atmospheric is
760 mmHg (100 kPa)
–
EVAP key–off monitor runs when all of the
following conditions met:
–
Atmospheric pressure
525 to 825 mmHg (70 to 110 kPa)
Battery voltage
10.5 V
–
Vehicle speed
–
4 km/h (2.5 mph)
Ignition switch
OFF
Engine condition
Not running
Time after engine stopped
5 hours
FTP sensor malfunction (P0450, P0452,
P0453)
Not detected
Purge VSV
Not operated by scan tool
Vent valve
Not operated by scan tool
Leak detection pump
Not operated by scan tool
Both of the following conditions are met
before IG switch OFF
Condition 1 and 2
1. Duration that vehicle is driven
5 min.
–
2. Purge flow
Executed
ECT
4.4 to 35
°
C (40 to 95
°
F)
IAT
4.4 to 35
°
C (40 to 95
°
F)
Example of re–start time
–
First time
7 hours
Second time
9 hours and 30 min.
Key–off monitor sequence
1 to 8
1. Atmospheric pressure
–
Next sequence is run if following condition
set
–
Atmospheric pressure change for 10 sec.
–
2.25 mmHg (0.3 kPa) for 1 sec.
2. First reference pressure
–
Next sequence is run if all of following
conditions set
Condition 1, 2 and 3
1. FTP when 4 sec. after reference pres-
sure measurement
–
–7.5 mmHg (–1 kPa)
2. Reference pressure
–36.38 to –7.93 mmHg (–4.85 to –1.057 kPa)
3. Reference pressure
Saturated
3. Vent valve stuck closed check
–
Next sequence is run if following condition
set
–
FTP change for 10 sec. after vent valve
ON (closed)
2.25 mmHg (0.3 kPa)
–
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