2001 TOYOTA HIGHLANDER o2 sensor

05-1 14
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
304 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
INSPECTION PROCEDURE
HINT:

If DTCs P0115, P0116, P0117, P0118 and P0125 are output simultaneously, engine coolant tempera-
ture sensor circuit may be open or short. Perform the troubleshooting of DTC P0115, P0117 or P0118
first.

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 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, and other data from the time the malfunction occurred.
1 CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0125)
(a) Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
Display (DTC Output)Proceed to
Only P0125 are outputA
P0125 and other DTCs are outputB
HINT:
If any other codes besides P0125 is output, perform the troubleshooting for those codes first.
B GO TO RELEVANT DTC CHART
(See page 05-48)
A
2 INSPECT THERMOSTAT (See page 16-2)
(a) Check the valve opening temperature of the thermostat.
OK:
Valve opening temperature: 80 to 84C (176 to 183F)
HINT:
Also check that the valve is completely closed under opening temperature as above.
NG REPLACE THERMOSTAT (See page 16-1 1)
OK
3 CHECK COOLING SYSTEM
(a) Check the cooling system for excessive cooling, such as abnormal radiator fan operation, modified
cooling system and other defects.
OK:
There is no modification of cooling system.
NG REPAIR OR REPLACE COOLING SYSTEM
OK
REPLACE ENGINE COOLANT TEMPERATURE SENSOR

A82385
ECTEstimated ECT
Threshold
(75C (167F))5 seconds
Indicated coolant temperature reading
Time
DTC set (after 2 driving cycles)
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-1 15
305 Author
: Date
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0128 COOLANT THERMOSTAT (COOLANT
TEMPERATURE BELOW THERMOSTAT
REGULATING TEMPERATURE)
CIRCUIT DESCRIPTION
This DTC is output when the Engine Coolant Temperature (ECT) does not reach 75°C (167°F) despite suffi-
cient engine warm-up time.
DTC No.DTC Detection ConditionTrouble Area
P0128
Conditions (a), (b) and (c) are met:
(a) Cold start
(b) Sufficient warm-up time has elapsed
(c) ECT is less than 75°C (167°F)
Thermostat

Cooling system

ECT sensor

ECM
MONITOR DESCRIPTION
The ECM estimates the coolant temperature based on starting temperature, engine loads, and engine
speeds. The ECM then compares the estimated temperature with the actual ECT. When the estimated cool-
ant temperature reaches 75C (167F), the ECM checks the actual ECT. If the actual ECT is less than 75C
(167F), the ECM will interpret this as a fault in the thermostat or the engine cooling system and set a DTC.
05ETK-05

05-1 16
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
306 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
MONITOR STRATEGY
Related DTCsP0128: Coolant thermostat
Required sensors/components (Main)Thermostat
Required sensors/components (Related)ECT sensor, IAT sensor, VSS
Frequency of operationOnce per driving cycle
Duration500 sec.
MIL operation2 driving cycles
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever this DTC is not presentSee page 05-16
Battery voltage11 V or more
Throttle position learningCompleted
Either of the following conditions is met:Condition 1 or 2
1. All of the following conditions are met:Condition (a), (b) and (c)
(a) ECT at engine start - IAT at engine start-15 to 7C (-27 to 12.6F)
(b) ECT at engine start-10 to 56C (14 to 132.8F)
(c) IAT at engine start-10 to 56C (14 to 132.8F)
2. All of the following conditions are met:Condition (a), (b) and (c)
(a) ECT at engine start - IAT at engine startMore than 7C (12.6F)
(b) ECT at engine start56C (132.8F) or less
(c) IAT at engine start-10C (14F) or more
Accumulated time that vehicle speed is 80 mph (128 km/h)
or moreLess than 20 seconds
TYPICAL MALFUNCTION THRESHOLDS
Duration that both of the following conditions 1 and 2 are
met:5 seconds or more
1. Estimated ECT120.5C (248.9F) or more
2. ECT sensor outputLess than 120.5C (248.9F)
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 $08: Thermostat
TLTCIDUnit ConversionDescription of Test DataDescription of Test Limit
1$01
Multiply by 0.625 and subtract
40
(C)ECT sensor output when estimated ECT
has reached to malfunction criterionMalfunction criteria for thermostat

A90870
Atmosphere
Housing
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platinum Electrode
Heater
Coating (Ceramic)
Exhaust Gas CoverIdeal Air-fuel Mixture
Output Voltage
Richer - Air Fuel Ratio - Leaner
05-1 18
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
308 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION
(BANK 1 SENSOR 2)
DTC P0137 OXYGEN SENSOR CIRCUIT LOW VOLTAGE
(BANK 1 SENSOR 2)
DTC P0138 OXYGEN SENSOR CIRCUIT HIGH VOLTAGE
(BANK 1 SENSOR 2)
CIRCUIT DESCRIPTION
The heated oxygen sensor (HO2S) is used to monitor oxygen in the exhaust gas. For optimum catalyst op-
eration, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S
output voltage changes suddenly in the vicinity of the stoichiometric ratio. The ECM adjusts the fuel injection
time so that the air-fuel ratio is nearly stoichiometric.
The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxy-
gen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S
voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The
ECM interprets Rich when the HO2S voltage is above 0.45 V.
05ITJ-02

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
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309 Author
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)DTC No.
DTC Detection ConditionTrouble Area

Following condition (a) (b) or (c) is met:
(a) During driving with engine warmed up, heated oxygen sen-
sor output does not change for 8 minutes
(b) Heated oxygen sensor output is very low most of time for

Open or short in heated oxygen sensor (bank 1 sensor 2)
ii
P0136
(b) Heated oxygen sensor out ut is very low most of time for
220 seconds
(c) The rear heated oxygen sensor voltage does not drop to
below 0.2 V immediately when vehicle decelerates and fuel
cut is operatingcircuit

Heated oxygen sensor (bank 1 sensor 2)

Heated oxygen sensor heater (bank 1 sensor 2)

A/F sensor


A/F sensor heatercut is o erating

Both (a) and (b) continue for more than 30 seconds:
(a) Estimated rear oxygen sensor temperature is less than
800C
(b) Rear oxygen sensor impedance is less than 5W
A/F sensor heater

EFI relay
P0137
Both (a) and (b) continue for more than 240 seconds:
(a) Estimated rear oxygen sensor temperature is more than
450C
(b) Rear oxygen sensor impedance is more than 15kW
Open or short in heated oxygen sensor (bank 1 sensor 2)
circuit (sensor to ECM)

Open or short in heated oxygen sensor (bank 1 sensor 2)
internal
P0138Rear oxygen sensor output voltage is over 1.2 V for more than
30 seconds
Short in heated oxygen sensor (bank 1 sensor 2) circuit

Short in heated oxygen sensor (bank 1 sensor 2) circuit

ECM internal circuit malfunction
MONITOR DESCRIPTION
The ECM monitors the rear heated oxygen sensor (HO2S) in the following 4 items:
1. The HO2S voltage changes between Rich (more than 0.45 V) and Lean (less than 0.45 V) while the vehicle
is running (repeating acceleration and deceleration) for 8 minutes. If not, the ECM interprets this as a mal-
function, illuminates the MIL, and then sets a DTC.
2. The HO2S voltage does not remain at less than 0.05 V for a long time while the vehicle is running (60 %
of the time in the 220 second-monitor, the sensor output is less than 0.05 V). If it does, the ECM interprets
this as a malfunction, illuminates the MIL, and then sets a DTC.
3. The sensor's voltage drops to below 0.2 V (extremely Lean status) immediately when the vehicle deceler-
ates and the fuel cut is working for 7 seconds. If not, the ECM interprets this to mean the sensor's response
feature has deteriorated, illuminates the MIL, and then sets a DTC.
4. The rear oxygen sensor impedance is 5 W or less, 15 kW or more, or output voltage is 1.2 V or more (normal
voltage: 0 to 1.0 V). If so, the ECM will determine that the rear oxygen sensor or a related circuit has an open
or short circuit, illuminates the MIL and sets a DTC.
Impedance is detected by the IC inside the ECM.
MONITOR STRATEGY
Related DTCs
P0136: Heated oxygen sensor output voltage (Output voltage)
P0136: Heated oxygen sensor impedance (Low impedance)
P0137: Heated oxygen sensor impedance (High impedance)
P0138: Heated oxygen sensor output voltage (High voltage)
P0138: Heated oxygen sensor output voltage (During fuel-cut)
Required Sensors/Components (Main)Heated oxygen sensor
Required Sensors/Components (Related)Crankshaft position sensor, engine coolant temperature sensor, mass air flow me-
ter and throttle position sensor
Frequency of OperationOnce per driving cycle: Active air-fuel ratio control detection
Continuous: Others
DurationWithin 480 seconds
MIL Operation
2 driving cycles: P0136 (Rear HO2S output voltage - case 1)
P0136 (Rear HO2S output voltage - case 2)
P0138 (Rear HO2S voltage during fuel-cut)
Immediate: Others
Sequence of OperationNone

A90296
MRELOX1B
31HT1BECM
FL
Main
BatteryEngine
Room R/B
No. 2
J2
J/C W-B B-W
4H10
Heated Oxygen Sensor
BR
BR A
A 1
12D
EFI
Relay35
2 2
5
31Engine
Room
J/BB
EEE5 E8
E8
8 21
29
2
O1B- Shielded
E91
E1 ABR J7
J/CE8
ABR
EH F7
FL
Block
AssyW
W22
EFI
NO. 2
2B
2F 2I EFI
NO. 12
IM13
IM16
IM1R-Y
G
R
B P-LW B-R
GR
Y2 1
34
13
IK3
IM1 4 IM1
EB15
1
R HT
OX
E +B
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
WIRING DIAGRAM

A58686
Vehicle speed
60 km/h
(38 mph)
Ignition Switch OFFOnce
40 seconds
or more
Warm up
(engine coolant
temperature
is more than 75C (167F)) 10 seconds
or moreTwice
40 seconds
or more12 times
40 seconds
or more
(a), (b)(d)
(e)
Idling (c)(d)
(e)(d)
(f)
10 seconds
or more10 seconds
or more 05-124
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
CONFIRMATION DRIVING PATTERN (P0136)
(a) Connect the hand-held tester to the DLC3.
(b) Switch the hand-held tester from normal mode to check (test) mode (see page 05-40).
(c) Start the engine and warm it up until the engine coolant temperature becomes more than 75C.
(d) Drive the vehicle at 60 km/h (38 mph) or more for 40 seconds or more.
(e) Let the engine idle for 10 seconds or more.
(f) Perform steps (d) to (e) 12 times.
HINT:
If a malfunction exists, the MIL will illuminate during step (f).
NOTICE:
If the conditions in this test are not strictly followed, detection of a malfunction will not occur. If you
do not have a hand-held tester, turn the ignition switch OFF after performing steps from (c) to (f), then
perform steps from (c) to (f) again.
CONFIRMATION DRIVING PATTERN (P0137)
Warm up the engine and run the engine at 60 km/h (38 mph) for 7 minutes.
CONFIRMATION DRIVING PATTERN (P0138)
Warm up the engine and run the engine at idle for 30 seconds.
INSPECTION PROCEDURE
HINT:
Hand-held tester only:
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 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).

+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)
Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25 % " rich output: Less than 3.0 V
-12.5 % " lean output: More than 3.35 V
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25 % " rich output: More than 0.55 V
-12.5 % " lean output: Less than 0.4 V
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 A/F CONTROL procedure enables a technician to check and graph the voltage outputs of both
the A/F sensor and the heated oxygen sensor.
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.
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.