engine coolant LEXUS SC400 1991 Service Manual PDF

11. RECONNECT DRIVER BELTInstall the drive belt by turning the drive belt tensioner clock-
wise.
12. RECONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
13. REFILL WITH ENGINE COOLANT
Knock Sensors
INSPECTION OF KNOCK SENSORS
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
CAUTION: Turn the ignition switch to ºLOCKº. Discon-
nect the cable from the negative (±) terminal of the bat-
tery. Wait at least 20 seconds before proceeding with
work.
±
EFI SYSTEM Electronic Control System (Water Temperature Sensor)FI±69
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INSPECTION OF EGR GAS
TEMPERATURE SENSOR
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ºLOCKº position and the negative (±) termi-
nal cable is disconnected from the battery.
2. DRAIN ENGINE COOLANT
3. REMOVE EGR VALVE (a) Disconnect the EGR gas temperature sensor.
(b) Disconnect the following hoses from the EGR valve:(1) Water by±pass hose (from ISC valve)
(2) Water by±pass hose (from rear water by±pass joint)
(c) Remove the two nuts, EGR valve and gasket.
4. REMOVE EGR VALVE ADAPTOR (a) Disconnect the EGR gas temperature sensor.
(b) Disconnect the PCV hose from the EGR valve adaptor.
(c) Remove the two bolts, two nuts, EGR valve adaptor andgasket. FI±103
EFI SYSTEM
± Electronic Control System (EGR Gas Temperature Sensor (USA Spec. only))
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9. REINSTALL EGR VALVE(a) Place a new gasket on the EGR valve adaptor.
NOTICE:
w Do not touch the adaptor and EGR valve surfaces of the
gasket with your hand.
w Align the port holes of the gasket and adaptor. Be careful
of the installation direction.
(b) Install the EGR valve with the two nuts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
(c) Connect the following hoses to the EGR valve:
(1) Water by±pass hose (from ISC valve)
(2) Water by±pass hose (from rear water by±pass joint)
(d) Connect the EGR gas temperature sensor.
10. RECONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
11. REFILL WITH ENGINE COOLANT FI±105
EFI SYSTEM
± Electronic Control System (EGR Gas Temperature Sensor (USA Spec. only))
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Voltage at Engine (& ECT) ECU Wiring Connectors
TerminalsConditionSTD voltage (V)
BATT (E9 ± 33) ± E1 (E10 ± 69)±10 ± 14
IGSW (E9 ± 1)
+B (E9 ± 31) ± E1 (E10 ± 69)IG SW ON10 ± 14
+B1 (E9 ± 32)
VC (E10 ± 41) ±E2 (E10 ± 65)±4.0 ± 6.0
IDL1 (E10 ± 64)E2 (E10 65)Throttle (or sub±throttle) valve fully closed1.0 or less
IDL2 (E10 ± 63)± E2 (E10 ± 65)IG SW ONThrottle (or sub±throttle) valve fully open10 ± 14
VTA1 (E10 ± 43)E2 (E10 65)Throttle (or sub±throttle) valve fully closed0.1 ± 1.0
VTA1 (E10 ± 42)± E2 (E10 ± 65)Throttle (or sub±throttle) valve fully open3.0 ± 6.0
KS (E10 ± 66)±E1 (E10 ± 69)IdlingPulse generation
THA (E10 ± 45)±E2 (E10 ± 65)IdlingIntake air temp. 20°C (68 °F)1.0 ± 3.0
THW (E10 ± 44)±E2 (E10 ± 65)IdlingEngine Coolant temp. 80 °C (176 °F)0.1 ± 1.0
STA (E10 ± 77)±E1 (E10 ± 69)Cranking6.0 or more
#10 (E10 ± 20)
#20 (E10 ± 19)E01 (E10 ± 80)
IG SW ON10 ± 14
#30 (E10 ± 18)±
E02 (E10 ± 79)
#40 (E10 ± 17)IdlingPulse generation
IGT1 (E10 ± 57)E1 (E10 69)IdlingPulse generationIGT2 (E10 ± 56)± E1 (E10 ± 69)IdlingPulse generation
IGF1 (E10 ± 58)E1 (E10 69)IdlingPulse generationIGF2 (E10 ± 59)± E1 (E10 ± 69)IdlingPulse generation
G1 (E10 ± 26)G1 ± (E10±6)IdlingPulse generationG2 (E10 ± 25)±
G2 ± (E10±5) IdlingPulse generation
NE (E10 ± 27)±G ± (E10 ± 7)IdlingPulse generation
M ± REL (E9 ± 24)±E1 (E10 ± 69)IG SW ON10 ± 14
FPC (E9 22)E1 (E10 69)Cranking, Sudden racing (6,000 rpm)4.2 ± 6.0FPC (E9 ± 22)± E1 (E10 ± 69)IdlingPulse generation
D1 (E9 ± 21)±E1 (E10 ± 69)Idling7.5 or more
FPU (E10 73)E1 (E10 69)IG SW ON10 ± 14FPU (E10 ± 73)± E1 (E10 ± 69)Restarting high temp.2.0 or less
PAG (E10 ± 74)±E01 (E10 ± 69)IG SW ON10 ± 14
Engine & ECT ECU Terminals
FI±131EFI SYSTEM
± Electronic Control System (Engine & ECT ECU)
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Resistance of ECU Wiring Connectors
TerminalsConditionSTD voltage (V)
#10 (E10 ± 20)
#20 (E10 ± 19)
#30 (E10 ± 18)+ B (E9 ± 31)13 2 14 2#40 (E10 ± 17)±+ B1 (E9 ± 32) ±13.2 ± 14.2
#50 (E10 ± 16)
#60 (E10 ± 15)
ISC1 (E10 ± 35)
ISC2 (E10 ± 34)+ B (E9 ± 31)10 30ISC3 (E10 ± 33)±
+ B1 (E9 ± 32) ±10 ± 30
ISC4 (E10 ± 32)
ACIS (E10 39)+ B (E9 ± 31)38 5 44 5ACIS (E10 ± 39)±
+ B1 (E9 ± 32) ±38.5 ± 44.5
HT (E10 71)+ B (E9 ± 31)51 63HT (E10 ± 71)±
+ B1 (E9 ± 32) ±5.1 ± 6.3
EVAP (E10 74)+ B (E9 ± 31)30 34EVAP (E10 ± 74)±
+ B1 (E9 ± 32) ±30 ± 34
ERG (E10 75)+ B (E9 ± 31)33 39ERG (E10 ± 75)±
+ B1 (E9 ± 32) ±33 ± 39
IDL1 (E10 ± 64)E2 (E10 65)Throttle valve openInfinity
IDL2 (E10 ± 63)± E2 ± (E10 ± 65)Throttle valve fully closed2,300 or less
VTA1 (E10 ± 43)E2 (E10 65)Throttle valve open3,300 ± 10,000
VTA2 (E10 ± 42)± E2 ± (E10 ± 65)Throttle valve fully closed200 ± 800
VC (E10 ± 41)±E2 ± (E10 ± 65)±4,000 ± 9,000
THA (E10 ± 45)±E2 ± (E10 ± 65)Intake air temp. 20
°C (68 °F)2,000 ± 3,000
THW (E10 ± 44)±E2 ± (E10 ± 65)Coolant temp. 80 °C (176 °F)200 ± 400
THG (E10 ± 46)±E2 ± (E10 ± 65)EGR gas temp. 50 °C (112 °F)69,400 ± 88,500
G1 (E10 ± 26)G (E10 7)Camposition sensor 10 + 40°C (14 104°F)125 190G2 (E10 ± 25)±G (E10 ± 7)Cam position sensor ± 10 ± + 40°C (14 ± 104°F)125 ± 190
NE (E10 ± 27)±G (E10 ± 7)Cam position sensor ± 10 ± + 40 °C (14 ± 104 °F)155 ± 240
Engine & ECT ECU Terminals
FI±134EFI SYSTEM ± Electronic Control System (Engine & ECT ECU)
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SERVICE DATA (Cont'd)
Water temp.
sensorResistanceat ±20°C (±4 °F)
at 0 °C (32 °F)
at 20 °C (68 °F)
at 40 °C (104 °F)
at 60 °C (140 °F)
at 80 °C (176 °F)10 ± 20 k

4 ± 7 k

2 ± 7 k

0.9 ± 1.3 k

0.4 ± 0.7 k

0.2 ± 0.4 k

EGR gas
temp.
sensorResistanceat 50°C (112 °F)
at 100 °C (212 °F)
at 150 °C (302 °F)69 ± 89 k

12 ± 15 k

2 ± 4 k

Main oxygen
sensorHeater coil resistance5.1 ± 6.3

Sub±oxygen
sensorHeater coil resistance5.1 ± 6.3

ECUHINT:

Perform all voltage and resistance measurements with the ECU connected.

Verify that the battery voltage in 11 V or above with the ignition switch is ON.
Voltage
TerminalsConditionSTD voltage (V)
BATT ± E1±10 ± 14
IGSW
+B ± E1
+B1
IG SW ON10 ± 14
VC ± E2±4.0 ± 6.0
IDL1E2
Throttle (or sub±throttle) valve fully closed1 or lessIDL1
IDL2 ± E2
IG SW ONThrottle (or sub±throttle) valve fully open10 ± 14
VTA1E2
Throttle (or sub±throttle) valve fully closed0.1 or lessVTA1
VTA 2 ± E2
Throttle (or sub±throttle) valve fully open3.0 ± 6.0
KS ± E1IdlingPulse generation
THA ± E2
THW±E2Idling
Intake air temp. 20
°C (68 °F)1.0 ± 3.0
THW ± E2IdlingEngine coolant temp. 80 °C (176 °F)0.1 ± 1.0
STA ± E1Cranking6.0 or more
#10
#20
E01IG SW ON10 ± 14#20
#30
#40±
E01
E02IdlingPulse generation
IGT1
IGT2
± E1IdlingPulse generation
FI±138EFI SYSTEM
± Service Specifications
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SERVICE DATA (Cont'd)
ECU (cont'd)Resistance of wiring connector side (cont'd)
TerminalsConditionSTD voltage (
)
±
HTR1
HTR2
HTL1
HTL2 +B
+B1±5.1 ± 6.3
±
PA G +B
+B1±30 ± 34
±IDL1 +BThrottle valve fully openInfinity
±IDL1
IDL2
+B
+B1Throttle valve fully closed2,300 or less
±VTA1E2
Throttle valve fully open3,300 ± 10,000
±VTA1
VTA2E2
Throttle valve fully closed200 ± 800
VC ± E2±4,000 ± 9,000
THS ± E2Intake air temp, 20
°C (68 °F)2,000 ± 3,000
THW ± E2Coolant temp. 80 °C (176 °F)200 ± 400
THG ± E2EGR gas temp. 50 °C (112 °F)69,400 ± 88,500
G1
G2 G1 (±)
G2 (±)
±Cam position sensor ± 10 ± +40
°C (14 ± 104 °F)835 ± 1,350
NE ± NE (±)engine speed sensor ± 10 ± +40 °C (14 ± 104 °F)835 ± 1,350
Fuel cut rpmw/ Vehicle speed 0 km/h and coolant temp. 80 °C (176 °F)
Fuel cut rpm
Fuel return rpm
1,800 rpm
1,400 rpm
FI±141EFI SYSTEM ± Service Specifications
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The EFI system is composed of three basic sub±systems: Fuel, Air Induction and Elect\
ronic Control
Systems.
FUEL SYSTEM
An electric pump fuel pressure supplies sufficient fuel, under a constant pressure, to the EFI injectors. In
accordance with signals from the ECU (Electronic Control Unit), these \
injectors inject the quantity of fuel most
appropriate for the engine condition into the intake manifold.
AIR INDUCTION SYSTEM
The air induction system provides sufficient air for engine operation.
ELECTRONIC CONTROL SYSTEM
The 1UZ±FE engine (ECU±formerly EFI computer) with a microcomputer \
centrally controls the EFI, ESA,
ISC and Diagnosis system, etc. The ECU controls the following functions:
1. Electronic Fuel Injection (EFI)
The ECU receives signals from various sensors indicating changing engine op\
eration conditions such as:Intake air volume
Intake air temperature
Coolant temperature
Engine rpm
Acceleration/deceleration
Exhaust oxygen content etc.
The signals are utilized by the ECU to determine the injection duration nec\
essary for an optimum air±fuel
ratio.
2. Electronic Spark Advance (ESA) The ECU is programmed with data for optimum ignition timing under any and all opera\
ting conditions. Using
data provided by sensors which monitor various engine functions (rpm, coola\
nt temperature, etc.), the
Electronic Control Unit (ECU) triggers the spark at precisely right instant. (S\
ee IG section)
3. Idle Speed Control (ISC) The ECU is programmed with idle speed data for various engine conditions (\
coolant temperature, air condi-
tioner ON/OFF, etc.).
The air volume flowing through the throttle valve by±pass passage is adj\
usted according to the signal from
each sensor and the idle speed is kept at the set value.
4. Diagnosis Function When the ECU detects any malfunctions or abnormalities in the sensor network\
, it lights the ºCHECKº en-
gine warning light in the combination meter. At the same time, the trouble is identified and a diagnostic code
is recorded by the ECU. The diagnostic code can be read by the number of\
blinks of the ºCHECKº engine
warning light when terminals TE1 and E1 are connected. The diagnostic co\
des are refer to the later page.
(See TR section)
5. Self±Correction Function If any sensor malfunctions, an average value recorded in the back±up ci\
rcuit is substituted to make driving
possible.
If danger is predicted, the engine is stopped and the ºCHECKº engine\
warning light will light up.
6. Fail±Safe Function Even if an abnormality occurs in the ECU, the back±up circuit uses a specifie\
d fuel injection and ignition
timing to provide vehicle driveability, and also lightsup the ºCHECKº engine warning light.
FI±4
EFI SYSTEM
± Description
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ELECTRONIC CONTROL SYSTEM
The control system consists of sensors which detect various engine conditio\
ns, and a ECU which determines
the injection volume (timing) based on the signals from the sensors.
The various sensors detect the air intake volume, engine rpm, oxygen densit\
y in the exhaust gas, coolant tem-
perature, air intake temperature and atmospheric pressure etc. and convert the inf\
ormation into an electrical
signal which is sent to the ECU. Based on these signals, the ECU calculates th\
e optimum ignition timing for the
current conditions and operates the injectors.
The ECU not only controls the fuel injection timing, but also the self diag\
nostic function which records the oc-
currence of a malfunction, ignition timing control, idle rpm control, EGR contro\
l, EVAP control, ACIS and fuel
pump control, which switches between the high and low fuel pump speeds accor\
ding to varied load conditions. FI±8
±
EFI SYSTEM Operation
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FUEL SYSTEM
Fuel is pumped up by the fuel pump, which flows through the fuel filter under pr\
essure through the fuel pipe
to the delivery pipe where it is distributed to each injector and the cold\
start injector.
The fuel pressure regulator adjusts the pressure of the fuel from the fuel \
line (high pressure side) to a pres-
sure 284 kPa (2.9 kgf/cm
2, 41 psi) higher than the pressure inside the intake manifold, and exce\
ss fuel is re-
turned to the fuel tank through the return pipe.
When the engine is hot, the fuel pressure is increased to control percolatio\
n in the fuel system and improve
restartability and idling stability.
The pulsation damper absorbs the slight fluctuations in fuel pressure ca\
used by the injector.
The injectors operate on input of injection signals from the ECU and inj\
ect fuel into the intake manifold.
The cold start injector operates when starting with low coolant temperature or at normal temperature
ranges, injecting fuel into the air intake chamber to improve startability. FI±7
EFI SYSTEM
± Operation
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