Toyota Sequoia (2005). Manual - part 115

Status
A/F S1

Status
O2S S2

A/F Condition and A/F and
HO2 Sensors Condition

Misfires

Main Suspected Trouble Areas

Proceed To

Lean

Lean/Rich

Normal

–



 Three–way Catalytic Converter (TWC)



 

Gas leakage from exhaust system

A

A

A

B

B

C

C

Lean/Rich

Lean/Rich

Lean/Rich

Lean/Rich

Lean/Rich

Lean

Lean

Rich

Rich

Rich

Rich

Lean

A/F sensor malfunction

A/F sensor malfunction

HO2 sensor malfunction

HO2 sensor malfunction

Actual air–fuel ratio lean

Actual air–fuel ratio lean

–

–

–

–

May occur



 A/F senso

r



 A/F sensor



 

HO2 sensor



 

HO2 sensor



 

Gas leakage from exhaust system



 

Gas leakage from exhaust system



 

Gas leakage from exhaust system



 

Gas leakage from exhaust system



 Extremely rich or lean actual air–fuel ratio

–



 Extremely rich or lean actual air–fuel ratio

–

DIAGNOSTICS

ENGINE

DI–255

449

Standard:

Tester Display

(Sensor)

Injection Volumes

Status

Voltages

AFS B1S1

(A/F)

+25 %

Rich

Less than 3.0

AFS B1S1

(A/F)

–12.5 %

Lean

More than 3.35

O2S B1S2

(HO2)

+25 %

Rich

More than 0.55

O2S B1S2

(HO2)

–12.5 %

Lean

Less than 0.4

RESULT:

Lean: During A/F CONTROL, the A/F sensor output voltage (AFS) is consistently more than 3.35 V, and the
HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
Rich: During A/F CONTROL, the AFS is consistently less than 3.0 V, and the O2S is consistently more than
0.55 V.

B

Check and replace A/F sensor.

C

Check and replace heated oxygen sensor and
check and repair exhaust gas leakage.

A

DI–256

–

DIAGNOSTICS

ENGINE

450

3

Check gas leakage on exhaust system.

OK:

No exhaust gas leakage.

NG

Repair or replace exhaust gas leakage point.

OK

Replace front and rear three–way catalytic
converter in the bank a malfunction is de-
tected.

–

DIAGNOSTICS

ENGINE

DI–257

451

DTC

P0441

Evaporative Emission Control System Incor-
rect Purge Flow

DTC SUMMARY

DTCs

Monitoring Items

Malfunction Detection Conditions

Trouble Areas

Detection

Timings

Detection

Logic

P0441

Purge VSV (Vacuum
Switching Valve)

 

stuck

open

Vacuum pump creates negative pressure
(vacuum) in EVAP system and EVAP sys-
tem pressure measured. 0.02 inch leak
pressure standard is measured at the start
and at the end of the leak check.
If stabilized pressure higher than [second
0.02 inch leak pressure standard x 0.2],
ECM determines that purge VSV stuck
open

Purge VSV

Connector/wire harness
(Purge VSV – ECM)

ECM

Pump module

Leakage from EVAP system

While ignition
Switch OFF

2 trip

P0441

Purge VSV

 

stuck closed

After EVAP leak check performed, purge
VSV turned ON (open), and atmospheric
air introduced into EVAP system. 0.02 inch
leak pressure standard is measured at the
start and at the end of the leak check.
If pressure does not return to near atmo-
spheric pressure, ECM determines that
purge valve stuck closed

Purge VSV

Connector/wire harness
(Purge VSV – ECM)

ECM

Pump module

Leakage from EVAP system

While ignition
Switch OFF

2 trip

P0441

Purge flow

While engine running, following conditions
successively met:

Negative pressure not created in EVAP
system when purge VSV turned ON
(open)

EVAP system pressure change less than
0.5 kPa (3.75 mmHg) when vent valve
turned ON (closed)

Atmospheric pressure change before and
after purge flow monitor less than 0.1 kPa
(0.75 mmHg)

Purge VSV

Connector/wire harness
(Purge VSV – ECM)

Leakage from EVAP line 
(Purge VSV – Intake manifold)

ECM

While engine
running

2 trip

CIRCUIT DESCRIPTION

The circuit description can be found in the EVAP (Evaporative Emission) Inspection Procedure (see page

DI–460

).

DID88–01

DI–258

–

DIAGNOSTICS

ENGINE

452

MONITOR DESCRIPTION

The two monitors, Key–Off and Purge Flow, are used to detect malfunctions relating to DTC P0441. The
Key–Off monitor is initiated by the ECM internal timer, known as the soak timer, 5 hours* after the ignition
switch is turned to OFF. The purge flow monitor runs while the engine is running.
1.

KEY–OFF MONITOR

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 then 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.