2001 TOYOTA HIGHLANDER thermostat

'05 HIGHLANDER_U (L/O 0409)
133
2005 HIGHLANDER from Nov. '04 Prod. (OM48570U)

Towing a trailer.
NOTICE

Do not remove the thermostat in
the engine cooling system as this
may cause the engine to overheat.
The thermostat is designed to con-
trol the flow of coolant to keep the
temperature of the engine within
the specified operating range.

Do not continue driving with an
overheated engine. See If your ve-
hicle overheatsº on page 336 in
Section 4.
The tachometer indicates engine speed
in thousands of rpm (revolutions per
minute). Use it while driving to select
correct shift points and to prevent en-
gine lugging and over- revving.
Driving with the engine running too fast
causes excessive engine wear and poor
fuel economy. Remember, in most cases
the slower the engine speed, the greater
the fuel economy.
NOTICE
Do not let the indicator needle get
into the red zone. This may cause
severe engine damage.
This meter displays the odometer and
two trip meters.
1. OdometerÐShows the total distance
the vehicle has been driven.
2. Two trip metersÐShow two different
distances independently driven since
the last time each trip meter was set
to zero.
You can use one trip meter to calculate
the fuel economy and the other to
measure the distance on each trip. All
trip meter data is cancelled if the elec-
trical power source is disconnected.
Tachometer Odometer and two trip meters

05MOJ-01
TLT CID Description of Test ValueUnit Conversion Description of Test Limit
Multiply by 0.625 and
subtract 40 [C]ECT sensor output when estimated ECT
has reached to malfunction criterionMalfunction criterion for thermostat 1 $01 05-24
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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
CHECKING MONITOR STATUS
NOTICE:
The monitor status (mode 6) is not applicable to the heated oxygen sensor (HO2S). However, HO2S
test values can be checked by O2S TEST RESULT (mode 5). Refer to page 05-22
1. Outline
The monitor results and the test values can be checked with the OBDII scan tool.
The engine control module (ECM) monitors the emissions-related components as the thermostat, catalyst
converter and evaporative emissions (EVAP), and determines whether they are functioning normally or not.
When finished monitoring, the ECM stores the monitor results and the test values.
The monitor result indicates whether the component is functioning normally or not. The test value is the value
that was used to determine the monitor result. If the test value is outside the test limit (malfunction criterion),
the ECM determines the component is malfunctioning. Some emissions-related components have multiple
test values to determine monitor result. If one of these test values is outside test limit, the ECM determines
the component is malfunctioning.
2. Description
The test value and test limit information are described as shown in the following table. This information is
included under ºMONITOR RESULTº in the emissions-related DTC sections:
TID $08: Thermostat

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 OBDII scan tools.

MONITOR RESULT
CATALYST#1 B1 . INCMP
CATALYST#1 B2 . INCMP
O2S HEAT B1S1 . INCMP
O2S HEAT B1S2 . INCMP
O2S HEAT B2S1 . INCMP
O2S HEAT B2S2 . INCMP
THERMOSTAT . . . . . PASS
Press [ENTER] to
Select the Label .
A82674
Thermostat malfunction
VAL. . . . . . . . . . . . . . 119.375C
LMT. . . . . . . . . . . . . . . 75.000C
TLT. . . . . . . . . . . . . . . . . . . . . . 1
[HELP] to notice
[EXIT] to return
A82675
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3. Procedure (using hand-held tester)
(a) Connect the hand-held tester to the DLC3.
(b) Turn the ignition switch and hand-held tester ON.
(c) Clear DTCs.
(d) Allow the vehicle to drive, in accordance with the applicable drive pattern described in the READINESS
MONITOR DRIVE PATTERN section (see page 05-26).
(e) Select the hand-held tester menus: DIAGNOSIS, EN-
HANCED OBDII, MONITOR INFO and MONITOR RE-
SULT. The monitor result appears after the component
name.

INCMP indicates the component has not been monitored
yet.

PASS indicates the component is functioning normally.

FAIL indicates the component is malfunctioning.
(f) Select the component and press ENTER. If the monitor
result has been PASS or FAIL, the accuracy test value ap-
pears.

VAL indicates the test value.

LMT indicates the test limit (malfunction criterion).

TLT indicates the test limit type.
(g) Compare the test value with the test limit.

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.

If the test value is on the borderline of the test limit, a mal-
function is concealed in the component.
HINT:
The monitor result might on rare occasions be PASS even if the
malfunction indicator lamp (MIL) is illuminated. This indicates
the system malfunctioned on a previous driving cycle. This
might be caused by an intermittent problem.

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2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0125 INSUFFICIENT COOLANT TEMPERATURE
FOR CLOSED LOOP FUEL CONTROL
CIRCUIT DESCRIPTION
Refer to DTC P0115 on page 05-95.
DTC No.DTC Detection ConditionTrouble Area

If ECT (engine coolant temperature) or IAT (intake air temper-
ature) is less than -19.45°C (-3°F) at engine start; 20 min-
utes or more after starting engine, ECT sensor value is 20°C
(68°F) or less (2 tripdetection logic)
P0125
(68°F) or less (2 trip detection logic)

If ECT and IAT are between -19.45°C (-3°F) and -8.34°C
(17°F) at engine start; 5 minutes or more after starting en-
gine, ECT sensor value is 20°C (68°F) or less (2 trip detec-
ti l i )

Cooling system

ECT sensor

Thermostat
tion logic)

If ECT and IAT greater than -8.34°C (17°F) at engine start; 2
minutes or more after starting engine, ECT sensor value is
20°C (68°F) or less (2 trip detection logic)
MONITOR DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is used to monitor the temperature of the engine coolant.
The resistance of the sensor varies with the actual coolant temperature. The ECM applies a voltage to the
sensor and the varying resistance of the sensor causes the signal voltage to vary. The ECM monitors the
ECT signal voltage after engine start-up.
If, after sufficient time has passed, the sensor still reports that the
engine is not warm enough for closed-loop fuel control, the ECM interprets this as a fault in the sensor or
cooling system and sets a DTC.
Example:
The ECT is 0C (32F) at engine start. After 5 minutes running time, the ECT sensor still indicates that the
engine is not warm enough to begin active feedback control of the air-fuel ratio. The ECM interprets this as
a fault in the sensor or cooling system and sets a DTC.
MONITOR STRATEGY
Related DTCsP0125: Insufficient ECT (Engine coolant temperature) for closed loop
Required sensors/components (Main)Thermostat, cooling sysem
Required sensors/components (Related)ECT sensor, MAF meter
Frequency of operationContinuous
Duration
2 minutes: Engine start ECT is -8.34C (17F) or more
5 minutes: Engine start ECT is -19.45 to -8.34C (-3 to 17F)
20 minutes: Engine start ECT is less than -19.45C (-3F)
MIL operation2 driving cycles
Sequence of operationNone
TYPICAL ENABLING CONDITIONS
The monitor will run whenever the following DTCs are not
presentSee page 05-16
Fuel cutOFF
EngineRunning
IdleOFF
TYPICAL MALFUNCTION THRESHOLDS
Time until ºactual ECTº reaches ºClosed Loop ECTº
2 minutes: Engine start ECT is -8.34C (17F) or more
5 minutes: Engine start ECT is -19.45 to -8.34C (-3 to 17F)
20 minutes: Engine start ECT is less than -19.45C (-3F)
05ESW-05

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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)
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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

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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

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
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307 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
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.
1 CHECK COOLING SYSTEM
(a) Check the cooling system for excessive cooling, such as abnormal radiator fan operation, modified
cooling system and other defects.
NG REPAIR OR REPLACE COOLING SYSTEM
OK
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
REPLACE ECM(See page 10-9)