2001 TOYOTA HIGHLANDER o2 sensor

A90874
Crankshaft
Position
Sensor
Camshaft
Position
SensorIGT1
IGF1
IGT2
IGT3
IGT4 ECM
No. 1 Spark Plug
No. 2 Spark Plug
No. 3 Spark Plug
No. 4 Spark Plug IgniterFrom Battery
Ignition Coil
TA C
To Tachometer Other Sensors
ECT Sensor
MAF Meter
Throttle Position Sensor
OthersNo. 2 Ignition
Coil with Igniter
No. 3 Ignition
Coil with Igniter
No. 4 Ignition
Coil with IgniterNo. 1 Ignition
Coil with Igniter
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-175
365 Author
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)DTC No.
DTC Detection ConditionTrouble Area
P0351
P0352
P0353
P0354
No IGF signal to ECM while engine is running
(1 trip detection logic)
Ignition system
Open or short in IGF1 and IGT circuits (1 throught 4) from
ignition coil assy to ECM
Ignition coil assy (No. 1 throught No. 4)
ECM

A82388
ECM
Time IgniterIgnition Coil
Normal
Circuit Open Ignition Signal
(IGT)
Ignition
Confirmation
Signal (IGF)IGFIGT
Malfunction
Ignition Coil with Igniter
05-176
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
MONITOR DESCRIPTION
If the ECM does not receive the IGF after sending the IGT, it interprets this as a fault in the igniter and sets
a DTC.
MONITOR STRATEGY
Related DTCs
P0351: Igniter (Cylinder 1) malfunction
P0352: Igniter (Cylinder 2) malfunction
P0353: Igniter (Cylinder 3) malfunction
P0354: Igniter (Cylinder 4) malfunction
Required sensors/ components (Main)Igniter
Required sensors / components (Related)CKP sensor
Frequency of operationContinuous
Duration0.256 sec. + 4 sparks
MIL operationImmediate
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever these DTCs are not presentSee page 05-16
Either of the following condition is met:Condition 1 or 2
1. Engine RPM1,500 rpm or less
2. StarterOFF
TYPICAL MALFUNCTION THRESHOLDS
IGF signalECM does not receive any IGF signal when ECM sends IGT signal to igniter

A85838
Waveform of A/F Sensor
Before CatalystWaveform of Heated Oxygen Sensor
After Catalyst Normal Catalyst
Deteriorated Catalyst Waveform of A/F Sensor
Before CatalystWaveform of Heated Oxygen Sensor
After Catalyst 3.5 V
3.0 V
3.5 V
3.0 V1.0 V
0.5 V
1.0 V
0.5 V
10 seconds 10 seconds
0 V 0 V 05-184
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW
THRESHOLD (BANK 1)
MONITOR DESCRIPTION
The ECM uses sensors mounted before and after the three-way catalyst (TWC) to monitor its efficiency. The
first sensor, an Air Fuel ratio (A/F) sensor, sends pre-catalyst A/F ratio information to the ECM. The second
sensor, a heated oxygen sensor (O2S), sends post-catalyst information to the ECM. The ECM compares
these two signals to judge the efficiency of the catalyst and the catalyst's ability to store oxygen. During nor-
mal operation, the TWC stores and releases oxygen as needed. The capacity to store oxygen results in a
low variation in the post-TWC exhaust stream as shown below.
If the catalyst is functioning normally, the waveform of the heated oxygen sensor slowly switches between
RICH and LEAN. If the catalyst is deteriorated, the waveform will alternate frequently between RICH and
LEAN. As the catalyst efficiency degrades, its ability to store oxygen is reduced and the catalyst output be-
comes more variable. When running the monitor, the ECM compares sensor 1 signals (A/F sensor) over a
specific amount of time to determine catalyst efficiency. The ECM begins by calculating the signal length for
both sensors (for the rear oxygen sensor, the ECM uses the output voltage signal length). If the oxygen sen-
sor output voltage signal length is greater than the threshold (threshold is calculated based on the A/F sensor
signal length), the ECM concludes that the catalyst is malfunctioning. The ECM will turn on the MIL and a
DTC will be set.
05EW2-05

A82718
Signal Length
Time Sensor
Output
Voltage Heated Oxygen Sensor Signal Length
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)DTC No.
DTC Detection ConditionTrouble Area
P0420
After engine and catalyst are warmed up, and while vehicle is
driven within set vehicle and engine speed, waveform of
heated oxygen sensor (bank 1 sensor 2) alternates frequently
between RICH and LEAN (2 trip detection logic)
Gas leakage in exhaust system

A/F sensor (bank 1 sensor 1)

Heated oxygen sensor (bank 1 sensor 2)

Three-way catalytic converter (Exhaust manifold)
HINT:

Sensor 1 is the sensor closest to the engine assembly.

Sensor 2 is the sensor farthest away from the engine assembly.
MONITOR STRATEGY
Related DTCsP0420: Catalyst deterioration
Required sensors / components (Main)Catalyst
Required sensors / components (Related)A/F sensor, Heated oxygen sensor (HO2S), IAT sensor, MAF meter, CKP sensor,
ECT sensor
Frequency of operationOnce per driving cycle
Duration150 sec. (30 sec. x 5)
MIL operation2 driving cycles
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever this DTC is not presentSee page 05-16
Accumulated time that the following conditions are met:30 sec.
Battery voltage11 V or more
IAT-10C (14F) or more
Idle statusOFF
MAF8 to 35 g/sec.
Engine RPMLess than 4,500 rpm
ECT75C (167F) or more
Rich experience after fuel cutYe s
Fuel system statusClosed Loop
A/F sensorActivated
Rear HO2SActivated
Estimated catalyst temperatureBoth of the following conditions 1 and 2 are met:
1. Upstream catalyst temperature500 to 900C (932 to 1,652F)
2. Downstream catalyst temperature350 to 900C (662 to 1,652F)

Engine Speed
3,000 rpm
Idling
IG SW OFF
Warmed upTime (a) 2,000 rpm
(b)(c) (d)
A90911
3 minutes or so
2 seconds
2 seconds
Check 05-186
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
TYPICAL MALFUNCTION THRESHOLDS
Rear HO2S locus length13 V or more (Varies with A/F sensor locus length)
Frequency of the monitor4 times
MONITOR RESULT
Refer to page 05-24 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 (see page 05-26).

TID (Test Identification Data) is assigned to each emissions-related component.

TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.

CID (Component Identification Data) is assigned to each test value.

Unit Conversion is used to calculate the test value indicated on generic OBD ll scan tools.
TID $01: Catalyst - Sensor 1 A/F sensor, Sensor 2 HO2S
TLTCIDUnit ConversionDescription of Test DataDescription of Test Limit
0$01Multiply by 0.0078
(no dimension)Catalyst deterioration level:
Determined by waveforms of A/F sensor
and HO2S
Malfunction criteria for catalyst deterioration
CONDITIONING A/F SENSOR AND HEATED OXYGEN SENSOR FOR TESTING
(a) Connect the hand-held tester or the OBD II scan tool to the DLC3.
(b) Start the engine and warm it up with all the accessories switched OFF until the Engine Coolant Temper-
ature (ECT) is stable.
(c) Run the engine at 2,500 to 3,000 rpm for about 3 minutes.
(d) When alternating the engine between 3,000 rpm and 2,000 rpm for 2 seconds respectively, check the
waveform of the oxygen sensor (bank 1 sensor 2).
INSPECTION PROCEDURE
HINT:
Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the
engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help deter-
mine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean
or rich, and other data from the time the malfunction occurred.

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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
1 CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0420)
(a) Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
Display (DTC Output)Proceed to
Only P0420 is outputA
P0420 and other DTCs are outputB
HINT:
If any other codes besides P0420 are output, perform the troubleshooting for those codes first.
B GO TO RELEVANT DTC CHART
(See page 05-48)
A
2 CHECK FOR EXHAUST GAS LEAKAGE
NG REPAIR OR REPLACE EXHAUST GAS
LEAKAGE POINT
OK
3 INSPECT AIR FUEL RATIO SENSOR (BANK 1 SENSOR 1) (See page 12-6)
NG REPLACE AIR FUEL RATIO SENSOR
OK
4 INSPECT HEATED OXYGEN SENSOR (See page 05-1 18)
OK: During air-fuel ratio feedback, the O2S's output alternates between rich and lean.
NG REPLACE HEATED OXYGEN SENSOR
OK
REPLACE EXHAUST MANIFOLD AND FRONT EXHAUST PIPE

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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
HINT:
Hand-held tester only:

The following procedure enables a technician to identify a trouble area if there is a malfunction in front
A/F sensor or rear heated oxygen sensors other than the catalyst converter, or the malfunction that
indicates the actual air-fuel ratio extremely RICH or LEAN.
It is possible the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The
A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble
areas are malfunctioning or not.
(a) Perform the ACTIVE TEST A/F CONTROL operation.
HINT:
The A/F CONTROL operation lowers the injection volume 12.5 % or increases the injection volume 25 %.
(1) Connect the hand-held tester to the DLC3 on the vehicle.
(2) Turn the ignition switch ON.
(3) Warm up the engine by running the engine speed at 2,500 rpm for approximately 90 seconds.
(4) Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
(5) Perform the A/F CONTROL operation with the engine idle (press the right or left button).
Result:
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume
+25 % " rich output: More than 0.5 V
-12.5 % " lean output: Less than 0.4 V

+25 %
-12.5 %
More than 3.35 V
Less than 3.0 V
Case 1
Case 2
Case 3
Case 4
Output voltage of A/F sensor
(sensor 1)
Injection volume
Output voltage
Output voltage of heated oxygen
sensor (sensor 2)Main suspect
trouble area
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
(A/F sensor, heater, A/F sen-
sor circuit)
+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
NGExtremely rich or lean actual
air-fuel ratio
(Injector, fuel pressure, gas
leakage in exhaust system,
etc.) OK
OK
OK
Almost
No reaction
Almost
No reaction
Almost
No reaction Almost
No reaction
'
Heated oxygen sensor
(heated oxygen sensor,
heater, heated oxygen sensor
circuit)
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
NOTICE:
The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about
20 seconds of delay at maximum.
The following of A/F CONTROL procedure enables a technician to check and graph the voltage outputs of
both the heated oxygen sensors.
For displaying the graph, enter ºACTIVE TEST / A/F CONTROL / USER DATAº, select ºAFS B1S1 and O2S
B1S2º by pressing ºYESº and push ºENTERº. Then press ºF4º.