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 

DI–18

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)

–