engine coolant LEXUS SC400 1991 Service Repair Manual

ELECTRONIC CONTROL SYSTEM
The control system consists of sensors which detect various engine conditions, and a ECU which deter\
-
mines the injection volume (timing) based on the signals from the sens\
ors.
The various sensors detect the air intake volume, engine rpm, oxygen densit\
y in the exhaust gas, coolant
temperature, air intake temperature and atmospheric pressure etc. and convert the in\
formation 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
occurrence of a malfunction, ignition timing control, idle rpm control, \
EGR control, EVAP control, fuel pressure
control and fuel pump control. FI±9
EFI SYSTEM
± Operation
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REMOVAL OF COLD START INJECTOR
(See Components on page FI±26)
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
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 (See page CO±6)
3. REMOVE THROTTLE BODY COVER (a) Remove the mounting cap nut.
(b) Loosen the two bolts, and remove the throttle bodycover.
4. DISCONNECT CONTROL CABLES FROM THROTTLE BODY
Disconnect the following cables:(1) Accelerator cable
(2) A/T throttle control cable
(3) (w/ Cruise Control System)
Cruise control actuator cable
5. REMOVE INTAKE AIR CONNECTOR (a) Disconnect the following hoses:(1) Air hose from ISC valve
(2) Air hose (from PS air control valve) from intake air connector
(b) Remove the bolt holding the intake air connector to the cylinder head cover.
(c) Loosen the two hose clamps.
(d) Disconnect the intake air connector from the throttle body and air cleaner hose, and remove the intake air
connector. FI±27
EFI SYSTEM
± Fuel System (Cold Start Injector)
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(b) Push the front side of the high±tension cord cover, andconnect the front side claw groove of the upper
high±tension cord cover to the claw of the lower
high±tension cord cover.
(c) Install the upper high±tension cord cover with the two bolts.
13. INSTALL INTAKE AIR CONNECTOR (a) Connect the end portions of the intake air connector tothe throttle body and air cleaner hose.
(b) Tighten the two hose clamps.
(c) Install the bolt holding the intake air connector to the
cylinder head cover.
(d) Connect the following hoses: (1) Air hose to ISC valve
(2) Air hose (from PS air control valve) to intake air con- nector
14. CONNECT CONTROL CABLES TO THROTTLE BODY Connect the following cables:(1) Accelerator cable
(2) A/T throttle control cable
(3) (w/ Cruise Control System) Cruise control actuator cable
15. INSTALL THROTTLE BODY COVER Install the throttle body cover and hose clamp with the two
bolts and cap nut.
16. C O N N E C T C A B L E TO N E G AT I V E T E R M I N A L O F BATTERY
17. FILL WITH ENGINE COOLANT (See page CO±7)
18. CHECK FOR FUEL LEAKS (See page FI±16) FI±41
EFI SYSTEM
± Fuel System (Cold Start Injector)
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REMOVAL OF THROTTLE BODY
(See Components on page FI±69)
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
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 (See page CO±6)
3. REMOVE THROTTLE BODY COVER (a) Remove the mounting cap nut.
(b) Loosen the two bolts, and remove the throttle bodycover.
4. DISCONNECT CONTROL CABLES FROM THROTTLE BODY
Disconnect the following cables:(1) Accelerator cable
(2) A/T throttle control cable
(3) (w/ Cruise Control System)
Cruise control actuator cable
5. REMOVE INTAKE AIR CONNECTOR (a) Disconnect the following hoses:(1) Air hose from ISC valve
(2) Air hose (from PS air control valve) from intake air connector
(b) Remove the bolt holding the intake air connector to the cylinder head cover.
(c) Loosen the two hose clamps.
(d) Disconnect the intake air connector from the throttle body and air cleaner hose, and remove the intake air
connector.
FI±70
EFI SYSTEM
± Air Induction System (Throttle Body)
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(d) Connect the following hoses:(1) Air hose to ISC valve
(2) Air hose (from PS air control valve) to intake air con-
nector
4. CONNECT CONTROL CABLES TO THROTTLE BODY Connect the following cables:(1) Accelerator cable
(2) A/T throttle control cable
(3) (w/ Cruise Control System) Cruise control actuator cable
5. INSTALL THROTTLE BODY COVER Install the throttle body cover and hose clamp with the two
bolts and cap nut.
6. CONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
7. FILL WITH ENGINE COOLANT (See page CO±7)FI±79
EFI SYSTEM
± Air Induction System (Throttle Body)
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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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