Toyota Tundra. Manual — part 1391

DESCRIPTION

The description can be found in the EVAP (Evaporative Emission) System. (See DESCRIPTION ).

INSPECTION PROCEDURE

Refer to the EVAP SYSTEM .

MONITOR DESCRIPTION

5 hours* after the ignition switch is turned off, the leak detection pump creates negative pressure (vacuum) in
the EVAP 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.

MONITOR DESCRIPTION

fuel tank



Leakage from
canister

P0456

EVAP small
leak

Leak detection pump creates negative
pressure (vacuum) in EVAP system
and EVAP system pressure measured.
Reference pressure measured at start
and at end of leak check.
If stabilized pressure higher than
second reference pressure, ECM
determines that EVAP system has
small leak.



Fuel tank cap
(loose)



Leakage from
EVAP line
(Canister -
Fuel tank)



Leakage from
EVAP line
(Purge VSV -
Canister)



Canister pump
module



Leakage from
fuel tank



Leakage from
canister

While
ignition
switch off

2 trip

Sequence

Operation

Description

Duration

-

ECM activation

Activated by soak timer 5, 7 or 9.5 hours after ignition switch
turned off.

-

Atmospheric

Vent valve turned OFF (vent) and EVAP system pressure
measured by ECM in order to register atmospheric pressure.

10

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

Fig. 169: Evaporative Emission Control System Operation Diagram

A

pressure
measurement

If pressure in EVAP system not between 70 kPa-a and 110
kPa-a (525 mmHg-a and 825 mmHg-a), ECM cancels EVAP
system monitor.

seconds

B

First reference
pressure
measurement

In order to determine reference pressure, leak detection pump
creates negative pressure (vacuum) through reference orifice
and then ECM checks if leak detection pump and vent valve
operate normally.

60

seconds

C

EVAP system
pressure
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 measured value as it will be used in leak check. If
EVAP pressure does not stabilize within 15 minutes, ECM
cancels EVAP system monitor.

15

minutes

(1)

D

Purge VSV monitor

Purge VSV opened and then EVAP system pressure measured
by ECM. Large increase indicates normality.

10

seconds

E

Second reference
pressure
measurement

After second reference pressure measurement, leak check
performed by comparing first and second reference pressure.
If stabilized system pressure higher than second reference
pressure, ECM determines that EVAP system leaking.

60

seconds

-

Final check

Atmospheric pressure measured and then monitoring result
recorded by ECM.

-

(1)

If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

a. P0455: EVAP gross leak

In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP system and the
EVAP system pressure is measured. If the stabilized system pressure is higher than [second reference
pressure x 0.2] (near atmospheric pressure), the ECM determines that the EVAP system has a large
leakage, illuminates the MIL and sets the DTC (2 trip detection logic).

b. P0456: EVAP very small leak

In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP system and the
EVAP system pressure is measured. If the stabilized system pressure is higher than the second reference
pressure, the ECM determines that the EVAP system has a small leakage, illuminates the MIL and sets
the DTC (2 trip detection logic).

Fig. 170: EVAP Pressure Graph - EVAP Very Small Leak

MONITOR STRATEGY

MONITOR STRATEGY

Required Sensors/Components

Purge VSV and canister pump module

Frequency of Operation

Once per driving cycle

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

P0455 (pattern 1), P0456:

TYPICAL ENABLING CONDITIONS

P0455 (pattern 2):

TYPICAL ENABLING CONDITIONS - P0455 (PATTERN 2)

Duration

Within 15 minutes (varies with amount of fuel in tank)

MIL Operation

2 driving cycles

Sequence of Operation

None

Monitor runs whenever following DTCs not present

None

Atmospheric pressure

70 to 110 kPa-a (525 to 825 mmHg-a)

Battery voltage

10.5 V or higher

Vehicle speed

Below 4 km/h (2.5 mph)

Ignition switch

Off

Time after key off

5 or 7 or 9.5 hours

Canister pressure sensor malfunction (P0451, P0452 and 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 following conditions met before key off

Conditions 1 and 2

1. Duration that vehicle driven

5 minutes or more

2. EVAP purge operation

Performed

ECT

4.4 to 35°C (40 to 95°F)

IAT

4.4 to 35°C (40 to 95°F)

Atmospheric pressure

70 to 110 kPa-a (525 to 825 mmHg-a)

Battery voltage

10.5 V or higher

Vehicle speed

Below 4 km/h (2.5 mph)

Ignition switch

Off

Canister pressure sensor malfunction (P0451, P0452 and 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 1 and 2 set before key off

-

1. Duration that vehicle has been driven

5 minutes or more

2. EVAP purge operation

Performed

ECT

4.4 to 40°C (40 to 104°F)

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra