TOYOTA SEQUOIA 2001 Service Repair Manual

± DIAGNOSTICSENGINE
DI±249
443 Author: Date:
2005 SEQUOIA (RM1146U)
DTC P0420 Catalyst System Efficiency Below Threshold
(Bank 1)
DTC P0430 Catalyst System Efficiency Below Threshold
(Bank 2)
MONITOR DESCRIPTION
The ECM uses the two sensors, mounted in front of and behind the Three±way Catalytic Converter (TWC),
to monitor its efficiency.
The first sensor, the Air±Fuel Ratio (A/F) sensor (sensor 1), sends pre±catalyst information to the ECM. The
second sensor, the Heated Oxygen (HO2) sensor (sensor 2), sends post±catalyst information to the ECM.
The ECM compares the information transmitted by these two sensors to determine the efficiency of the TWC
performance and its ability to store oxygen.
When the TWC is functioning properly, the variation in the oxygen concentration in the exhaust gas, after
it has passed through the TWC, is small. In this condition, the voltage output of sensor 2 slowly alternates
between the rich and lean signal voltages (shown in the illustration below). As the TWC performance efficien-
cy deteriorates, its oxygen storage capacity decreases, and the variation in the oxygen concentration in the
exhaust gas increases. As a result, the sensor voltage output fluctuates frequently.
While the catalyst monitor is running, the ECM measures the signal lengths of both sensors 1 and 2, and
calculates the ratio of the signal lengths to determine the extent of the TWC deterioration. If the deterioration
level exceeds the preset threshold, the ECM interprets this as the TWC malfunction. The ECM then illumi-
nates the MIL and sets the DTC.
DTC No.DTC Detecting ConditionTrouble Area
P0420
P0430OSC value smaller than standard value under active air±fuel
ratio control (2 trip detection logic)
Gas leakage on exhaust system
A/F sensor (Bank 1, 2 sensor 1)
Heated oxygen sensor (bank 1, 2 sensor 2)
Three±way catalytic converter
HINT:
Bank 1 refers to the bank that includes cylinder No.1.
Bank 2 refers to the bank that does not include cylinder No.1.
Sensor 1 refers to the sensor mounted in front of the Three±Way Catalytic Converter (TWC) and lo-
cated near the engine assembly.
Sensor 2 refers to the sensor mounted behind the TWC and located far from the engine assembly.
DID87±01

DI±250
± DIAGNOSTICSENGINE
444 Author: Date:
2005 SEQUOIA (RM1146U)
MONITOR STRATEGY
RltdDTCP0420Bank 1 catalyst is deterioratedRelated DTCsP0430Bank 2 catalyst is deteriorated
Main sensors/componentsFront and rear heated oxygen sensor
Required sensors/componentsRelated sensors/components
Mass air flow meter, Engine coolant temperature
sensor, Engine speed sensor, Intake air tempera-
ture sensor
Frequency of operationOnce per driving cycle
Duration20 sec.
MIL operation2 driving cycles
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
ItSpecificationItemMinimumMaximum
The monitor will run whenever these
DTCs are not presentSee page DI±18
Battery voltage11 V±
Intake air temperature±10C (14F)±
Engine coolant temperature75°C (167°F)±
Atmospheric pressure coefficient0.75±
IdleOFF
Engine RPM±3,200 rpm
A/F sensorActivated
Fuel system statusClosed loop
Engine load10 to 70 %
All of the following conditions are metCondition 1, 2 and 3
1. MAF6to 75 g/sec
2. Front catalyst temperature (estimated)620to 830C (1,148 to 1,526F)
3. Rear catalyst temperature (estimated)410 to 830C (770 to 1,526F)
Rear HO2S monitorCompleted
Shift position4th±
TYPICAL MALFUNCTION THRESHOLDS
Detection CriteriaThreshold
Oxygen storage capacity (OSC) of catalystLess than 0.16

A23541
At least 3 minutes
2 seconds
Check
2 seconds
Engine Speed
3,000 rpm
2,000 rpm
Idling
Ignition Switch OFF(a)(b)(c) (d)
Time
Warming up(d)
± DIAGNOSTICSENGINE
DI±251
445 Author: Date:
2005 SEQUOIA (RM1146U)
MONITOR RESULT
Refer to page DI±26 for detailed information.
The test value and test limit information are described as shown in the following table. Check the monitor
result and test values after performing the monitor drive pattern (refer to ºConfirmation Monitorº).
MID (Monitor Identification Data) is assigned to each emissions±related component.
TID (Test Identification Data) is assigned to each test value.
Scaling is used to calculate the test value indicated on generic tools.
Catalyst bank 1 ± Active A/F control method
MIDTIDScalingDescription of Test ValueMinimum Test LimitMaximum Test Limit
$21$A9Multiply by 0.0003
(no dimension)Oxygen storage capacity of catalystMinimum test limit for catalystMaximum test limit for catalyst
Catalyst bank 2 ± Active A/F control method
MIDTIDScalingDescription of Test ValueMinimum Test LimitMaximum Test Limit
$22$A9Multiply by 0.0003
(no dimension)Oxygen storage capacity of catalystMinimum test limit for catalystMaximum test limit for catalyst
WAVEFORMS OF AIR±FUEL RATIO (A/F) AND HEATED OXYGEN (HO2) SEN-
SORS
HINT:
Perform the operation with the engine speeds and time durations described below prior to check the wave-
forms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropri-
ate inspection results.
(a) Connect the hand±held tester to the DLC3.
(b) Start the engine and warm it up with all the accessories switched OFF, until the engine coolant temper-
ature stabilizes.
(c) Run the engine at an engine speed of between 2,500 rpm and 3,000 rpm for at least 3 minutes.
(d) After confirming that the waveform of the heated oxygen sensor (bank 1, 2 sensor 1 (HA1A, HA2A)),
oscillate around 0.5 V during feedback to the ECM, check the waveform of the heated oxygen sensor
(bank 1, 2 sensor 2 (OX1B, OX2B)).

A23542
Normal Catalyst Deteriorated Catalyst
Waveform of
A/F Sensor
in front of TWC
Waveform of
HO2 Sensor
behind TWCVoltage output when active air±fuel ratio control not performed
3.5 V
3.0 V
1.0 V
0 V
10 seconds 10 seconds DI±252
± DIAGNOSTICSENGINE
446 Author: Date:
2005 SEQUOIA (RM1146U)
HINT:
If either of the voltage outputs of the Air±Fuel Ratio (A/F) or Heated Oxygen (HO2) sensors does not
fluctuate, or either of the sensors makes a noise, the sensor may be malfunctioning.
If the voltage outputs of both the sensors remain lean or rich, the air±fuel ratio may be extremely lean
or rich. In such cases, perform the following A/F CONTROL using a hand±held tester.
If the Three±Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the
TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active
air±fuel ratio control is not performed).
A/F CONTROL
HINT:
Hand±held tester only:
Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE
TEST. The A/F CONTROL function can help to determine whether the Air±Fuel Ratio (A/F) sensor, Heated
Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.
The following instructions describe how to conduct the A/F CONTROL operation using a hand±held tester.
(1) Connect a hand±held tester to the DLC3.
(2) Start the engine and turn the tester ON.
(3) Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
(4) On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE
TEST / A/F CONTROL.
(5) Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT
or LEFT button to change the fuel injection volume).
(6) Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and OS2 B1S2) displayed
on the tester.
HINT:
The A/F CONTROL operation lowers the fuel injection volume by 12.5 % or increases the injection
volume by 25 %.
Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

+25 %
±12.5 %
More than 3.35 V
Less than 3.0 V
1
A/F Sensor (Sensor 1)
Output Voltage
Injection volume
Output voltage
HO2 Sensor (Sensor 2)
Output VoltageMain Suspected
Trouble Areas
OK
+25 %
±12.5 %
More than 3.35 V
Less than 3.0V
Injection volume
Output voltage
+25 %
±12.5 %
More than 0.55 V
Less than 0.4V
Injection volume
Output voltage
A/F sensor+25 %
±12.5 %
More than 0.55 V
Less than 0.4V
Injection volume
Output voltage
+25 %
±12.5 %
Injection volume
Output voltage
NG
+25 %
±12.5 %
Injection volume
Output voltage
NG
+25 %
±12.5 %
Injection volume
Output voltage
NG
+25 %
±12.5 %
Injection volume
Output voltage
NG OK
OK
OK
Almost
no reaction
'
Almost
no reaction Almost
no reaction
Almost
no reaction
Case
2
3
4
A/F sensor circuit A/F sensor heater
HO2 sensor
HO2 sensor circuit HO2 sensor heater
(Air±fuel ratio extremely
lean or rich)Injector
Gas leakage from
exhaust system Fuel pressure
± DIAGNOSTICSENGINE
DI±253
447 Author: Date:
2005 SEQUOIA (RM1146U)
Standard:
Tester Display
(Sensor)Injection VolumesStatusVoltages
AFS B1S1
(A/F)+25 %RichLess than 3.0
AFS B1S1
(A/F)±12.5 %LeanMore than 3.35
O2S B1S2
(HO2)+25 %RichMore than 0.55
O2S B1S2
(HO2)±12.5 %LeanLess than 0.4
NOTICE:
The Air±Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2)
sensor has a maximum output delay of approximately 20 seconds.
Following the A/F CONTROL procedure enables technicians to check and graph the voltage outputs
of both the A/F and HO2 sensors.
To display the graph, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD
II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2, and press the YES but-
ton and then the ENTER button followed by the F4 button.

DI±254
± DIAGNOSTICSENGINE
448 Author: Date:
2005 SEQUOIA (RM1146U)
INSPECTION PROCEDURE
HINT:
Read freeze frame data using the hand-held tester. Freeze frame data records the engine conditions when
a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was
running or stopped, if the engine was warmed up or not, if the air±fuel ratio was lean or rich, as well as other
data from the time when a malfunction occurred.
1 Are there any other codes (besides DTC P0420 or P0430) being output?
PREPARATION:
(a) Connect the hand±held tester to the DLC3.
(b) Turn the ignition switch ON and push the hand±held tester main switch ON.
(c) When using hand±held tester, enter the following menu: DIAGNOSIS / ENHANCED OBD II / DTC
INFO / CURRENT CODES.
CHECK:
Read the DTC using the hand±held tester.
RESULT:
Display (DTC Output)Proceed to
ºP0420 and/or P0430ºA
ºP0420 or P0430º and other DTCsB
HINT:
If any other codes besides ºP0420 and/or P0430º are output, perform the troubleshooting for those DTCs
first.
B Go to relevant DTC chart (See page DI±58).
A
2 Check A/F sensor (bank 1, 2 sensor 1).
(a) Connect the hand±held tester to the DLC3.
(b) Start the engine and turn the tester ON.
(c) Warm up the engine with the engine speed at 2,500 rpm for approximately 90 seconds.
(d) On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST /
A/F CONTROL.
(e) Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT or LEFT
button to change the fuel injection volume).
(f) Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2) displayed on the
tester.
HINT:
The A/F CONTROL operation lowers the fuel injection volume by 12.5 % or increases the injection
volume by 25 %.
Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

Status
A/F S1Status
O2S S2A/F Condition and A/F and
HO2 Sensors ConditionMisfiresMain Suspected Trouble Areas
Proceed To
LeanLean/Rich Normal
± Three±way Catalytic Converter (TWC)
 Gas leakage from exhaust systemA
A A B
B
C
C Lean/Rich
Lean/Rich
Lean/Rich
Lean/Rich Lean/Rich
Lean Lean Rich
Rich
Rich
Rich LeanA/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
± DIAGNOSTICSENGINE
DI±255
449 Author: Date:
2005 SEQUOIA (RM1146U)
Standard:
Tester Display
(Sensor)Injection VolumesStatusVoltages
AFS B1S1
(A/F)+25 %RichLess than 3.0
AFS B1S1
(A/F)±12.5 %LeanMore than 3.35
O2S B1S2
(HO2)+25 %RichMore than 0.55
O2S B1S2
(HO2)±12.5 %LeanLess 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
± DIAGNOSTICSENGINE
450 Author: Date:
2005 SEQUOIA (RM1146U)
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.

± DIAGNOSTICSENGINE
DI±257
451 Author: Date:
2005 SEQUOIA (RM1146U)
DTC P0441 Evaporative Emission Control System Incor-
rect Purge Flow
DTC SUMMARY
DTCsMonitoring ItemsMalfunction Detection ConditionsTrouble AreasDetection
TimingsDetection
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 OFF2 trip
P0441Purge 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 OFF2 trip
P0441Purge 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
running2 trip
CIRCUIT DESCRIPTION
The circuit description can be found in the EVAP (Evaporative Emission) Inspection Procedure (see page
DI±460).
DID88±01

DI±258
± DIAGNOSTICSENGINE
452 Author: Date:
2005 SEQUOIA (RM1146U)
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 35C (95F) 5 hours after the ignition switch is turned off,
the monitor check starts 2 hours later. If it is still not below 35C (95F) 7 hours after the ignition switch is
turned off, the monitor check starts 2.5 hours later.
SequenceOperationsDescriptionsDuration
±ECM activationActivated by soak timer, 5 hours (7 or 9.5 hours) after ignition switch turned to OFF.±
AAtmospheric 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-
mentIn 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
CEVAP 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*
DPurge VSV monitorPurge VSV opened and then EVAP system pressure measured by ECM.
Large increase indicates normal.10 seconds
E
Second 0.02 inch leak
pressure measure-
mentLeak 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
FFinal checkAtmospheric 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.