sensor TOYOTA CAMRY 2000 Service Manual Online

CIRCUIT DESCRIPTION
The engine coolant temperature sensor senses the
engine coolant temperature. A thermistor built in the
sensor changes its resistance value according to the
engine coolant temperature. The lower the engine
coolant temperature, the greater the thermistor resis±
tance value, and the higher the engine coolant tem±
perature, the lower the thermistor resistance value
(See Fig. 1.).
The engine coolant temperature sensor is connected
to the ECM (See next page). The 5 V power source
voltage in the ECM is applied to the engine coolant
temperature sensor from the terminal THW via a resis-
tor R. That is, resistor R and the engine coolant tem±
perature sensor are connected in series. When the
resistance value of the engine coolant temperature
sensor changes in accordance with changes in the
engine coolant temperature, the potential at the ter±
minal THW also changes. Based on this signal, the
ECM increases the fuel injection volume to improve
driveability during cold engine operation. If the ECM
detects the diagnostic trouble code 22, it operates the
fail safe function in which the engine coolant temper±
ature is assumed to be 80
C (176
F).
w
Open or short in engine coolant temp,
sensor circuit
wEngine coolant temp. sensor
wECM Open or short in engine coolant temp. sensor
circuit for 0.5 sec. or more.Diagnostic Trouble Code Detecting Condition
Engine coolant
Temp.
C (
F)Resistance
(k
)
( Reference )
Voltage
(V)
Trouble Area 100 (212)
DTC 22 Engine coolant Temp. Sensor Circuit
60 (140) 40 (104)
80 (176) ±20 (±4)
DTC No.20 (68)0 (32)16.0
0.9
0.3 0.6
0.20.3 0.54.3
2.53.4
5.9
2.4
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±356

DIAGNOSTIC CHART
HINT If diagnostic trouble codes ª22º (engine coolant temperature sensor circuit), ª24º (intake air temperature sensor cir-
cuit), ª31º (manifold absolute pressure sensor circuit) and ª41º (throttle position sensor circuit) are output simultaneously, E2
(sensor ground) may be open, OK Check for momentary interruption
Check for open and short in harness and connector
between ECM and engine coolant temp. sensor.Check for momentary interruption
(See page EG1±309).
Repair or replace harness or
connector.Replace engine coolant temp. sensor.
WIRING DIAGRAM
Check resistance of sensor.
Check and replace ECM.Check voltage of sensor.
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±357

INSPECTION PROCEDURE
HINT: If diagnostic trouble codes ª22º (engine coolant temperature sensor circuit), ª24º (intake air
temperature sensor circuit), ª31º (manifold absolute pressure sensor circuit) and ª41 ª (throttle
position sensor circuit) are output simultaneously, E2 (sensor ground) may be open,
(1) Remove glove compartment
(See page EG1±234)
(2) Turn ignition switch on.
Measure voltage between terminals THW and E2 of engine
control module connector.
Check voltage between terminals THW and E2 of engine control
module connector.
Check for momentary interruption
(See page EG1±309)
Engine Coolant Temp.
C (
F)
20 (68)
( Engine is cool )
80 (176)
(Engine is hot)0.2 ~1.0 v 0.5 ~ 3.4 V Voltage
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±358

Check for open and short in harness and connector between engine
control module and engine coolant temp. sensor (See page IN±31).
Disconnect the engine coolant temp. sensor con±
nector.
Measure resistance between terminals.
Resistance is within Acceptable Zone on chart.
Check engine coolant temp. sensor.
Check and replace engine control module.Repair or replace harness or connector.Replace engine coolant temp. sensor.
Engine coolant
Temp.
C (
F)
0.2 ± 0.4 k
Resistance
80(176)20(68)
2 ± 3 k

± 5S±FE ENGINECIRCUIT INSPECTIONEG1±359

DIAGNOSTIC CHART
HINT: If diagnostic trouble codes ª22º (engine coolant temperature sensor circuit), ª24º (intake air
temperature sensor circuit), ª31º (manifold absolute pressure sensor circuit) and ª41º (throt±
tle position sensor circuit) are output simultaneously, E2 (sensor ground) may be open.
CIRCUIT DESCRIPTION
The intake air temp. sensor is built into the air cleaner cap and senses the intake air tempera-
ture. The structure of the sensor and connection to the ECM is the same as in the engine coolant
temp. sensor shown on page EG1±356.
If the ECM detects the diagnostic trouble code ª24º, it operates the fail safe function in which the
intake air temperature is assumed to be 20

C (68
F)
w
Open or short in intake air temp. sensor circuit.
wIntake air temp. sensor
wECM
Check for open and short in harness and
connector between ECM and intake air temp.
sensor.Open or short in intake air temp. sensor circuit
for 0.5 sec. or more.
Check for momentary
interruption (See page EG1±309). Diagnostic Trouble Code Detecting Condition
Repair or replace harness or
connector.Replace intake air temp. sensor.
WIRING DIAGRAM
Check resistance of sensor.
Check and replace ECM. Check voltage of sensor.Trouble Area
DTC 24 Intake Air Temp. Sensor Circuit
DTC No.
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±360

Check for open and short in harness and connector between
engine control module and intake air temp. sensor (See page IN±31).
Disconnect the air temp. sensor connector.
Measure resistance between terminals.
Resistance is within Acceptable Zone on chart.
Check intake air temp. sensor.
Check and replace engine control module.Repair or replace harness or connector.Replace intake air temp. sensor.
Intake air temp.
5C (5 F)
0.4 ± 0.7 k


Resistance
60 (140)20(68)
2 ±3k


± 5S±FE ENGINECIRCUIT INSPECTIONEG1±362

CIRCUIT DESCRIPTION
The main oxygen sensor is located in the exhaust manifold.
It indirectly determines whether the fuel mixture is rich or lean by detecting the concentration of
oxygen present in the exhaust gas.
Engine speed varies by more than 15 rpm over
the preceding crank position period during a period
of 50 sec. or more under conditions (a) and (b).
(2 trip detection logic) *
(a) Engine speed: Idling
(b) Engine coolant temp.: 60
C (140
F) or more (2) Engine speed varies by more than 15 rpm
over the preceding crank position period during
a period of 50 sec. or more under conditions
(a) and (b).
(2 trip detection logic) *
(a) Engine speed: Idling
(b) Engine coolant temp.: 60
C (140
F) or more.wOpen or short in injector circuit
wFuel line pressure (injector leak, blockage)
wMechanical system malfunction
(skipping teeth of timing belt)
wIgnition system
wCompression pressure
(foreign object caught in valve)
wAir leakage
wECM
wOpen or short in injector circuit
wFuel line pressure (injector leak, blockage)
wMechanical system malfunction
(skipping teeth of timing belt)
wIgnition system
wCompression pressure
(foreign object caught in valve)
wAir leakage
wECM (1) Main oxygen sensor voltage is 0.45 V or
less (lean) for 90 sec. under conditions (a)
and (b).
(2 trip detection logic) *
(a) Engine coolant temp.: 60
C (140
F) or more.
(b) Engine speed: 1,500 rpm or more.wOpen or short in main oxygen sensor circuit
wMain oxygen sensor
wIgnition system
w ECM Diagnostic Trouble Code Detecting Condition
*: See page EG1±307Trouble Area
DTC 25 26 Air±Fuel Ratio Lean Rich Malfunction
DTC No.
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±363

H I NT: Before this test, check the feedback voltage for oxygen sensor.
Disconnect the EFI fuse (15 A) for 10 sec. or more, with IG switch OFF.
Initiate test mode (Connect terminal TE2 and E1 of data link connector 1 or 2 with
IG switch OFF).
Start engine and warm up.
After the engine is warmed up, let it race at 2,500 rpm for 3 min.
After performing the racing in (3) , perform idling 1 min.
HINT: If a malfunction exists, the malfunction indicator lamp will light up during step (4).
NOTICE: If the conditions in this test are not strictly followed, detection of the malfunction
will not be possible.
CIRCUIT DESCRIPTION (Cont'd)
DIAGNOSIS TROUBLE CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
(b) To check that the malfunction is corrected when the repair is completed confirming that diagnostic
trouble code is no longer detected.
Malfunction: Open or Short in Main Oxygen Sensor.
Open or Short in Injector Circuit, Injector Leak or Blockage.
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±364

WIRING DIAGRAM
Refer to page EG1±354 for the WIRING DIAGRAM.
Does malfunction disappear when a good main
oxygen sensor is installed?Check each item found to be a possible cause
of problem.
Does malfunction disappear when a good main
oxygen sensor is installed?Check each item found to be a possible cause
of problem.Check for open and short in harness and
connector.Repair or replace harness or
connector.
DIAGNOSTIC CHART
Check voltage of terminal OX1.Check voltage of terminal VF1.
Replace main oxygen sensor.
Replace main oxygen sensor. Check and replace ECM.
Check and replace ECM.Check compression.
Check compression.Repair or replace.
Repair or replace.Repair or replace.
Repair or replace.N G TypeII
NG Type I
YESYES
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±365

(1) Warm up engine at normal operating tem±
perature.
(2) Connect terminals TE1 and E1 of data link
connector 1.
(3) Connect positive prove to terminal VF1 and
negative prove to terminal E1 of data link
connector 1.
(1) Warm up the oxygen sensor by running en±
gine at 2,500 rpm for about 2 minutes.
(2) Then, maintaining engine at 2,500 rpm,
count how many times needle of voltmeter
fluctuates between 0 and 5 V.
Warm up engine at normal operating temperature.
Measure voltage between terminals OX1 and E1
of data link connector 1 when engine is suddenly
raced to full throttle.
The voltage should be 0.5 V or higher at least
once.
Perform inspection within 1 second.
Check voltage between terminals OX1 and E1 of data link connector 1.
Check voltage between terminals VF1 and E1 of data link connector 1.
Needle fluctuates of 8 times or more
for every ten seconds
INSPECTION PROCEDURE
Continue at 0 V
Continue at 5 V
NG
Type II
Go to stepGo to step NG
Type
ING Type II
NG Type II Result
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±366