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
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.
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