1991 LEXUS SC400 engine

B. Inspect voltage of engine & ECT ECUCheck the voltage between each terminal.w Turn the ignition switch ON.
w Measure the voltage at each terminal.
HINT:
w Perform all voltage measurements with the connectors
connected.
w Verify that the battery voltage is 11 V or more when the
ignition switch is ON.
FI±130EFI SYSTEM ± Electronic Control System (Engine & ECT ECU)
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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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Voltage at Engine (& ECT) ECU Wiring Connectors (Cont'd)
TerminalsConditionSTD voltage (V)
ISC1 (E10 ± 35)
ISC2 (E10 ± 34)E1 (E10 69)IG SW ON10 14ISC3 (E10 ± 33)± E1 (E10 ± 69)IG SW ON10 ± 14
ISC4 (E10 ± 32)
VF1 (E10 ± 29)E1 (E10 69)Maintain engine speed at 2,500 rpm for 120 seconds10 40VF2 (E10 ± 28)± E1 (E10 ± 69)Maintain engine s eed at 2,500 rm for 120 seconds
after warming up then return to idling1.0 ± 4.0
OX1 (E10 ± 48)E1 (E10 69)Maintain engine speed at 2,500 rpm for 120 secondsPulse generation
OX2 (E10 ± 47)± E1 (E10 ± 69)Maintain engine s eed at 2,500 rm for 120 seconds
after warming up
Pulse generation
(0 ± 1.0)
HT (E10 ± 71)±E01 (E10 ± 80)Idle2.0 or less
KNK1 (E10 ± 50)E1 (E10 69)IdlePulse generationKNK2 (E10 ± 49)± E1 (E10 ± 69)IdlePulse generation
NSW (E10 76)E1 (E10 69)IG SW ONShift position ªPº or ªNº range1.0 or lessNSW (E10 ± 76)± E1 (E10 ± 69)IG SW ONEx. shift position ªPº or ªNº range10 ± 14
SP1 (E9 ± 2)±E1 (E10 ± 69)IG SW ONRotate driving wheel slowly.4 or more
TE1 (E9 ± 20)E1 (E10 69)IG SW ON10 14TE2 (E9 ± 19)± E1 (E10 ± 69)IG SW ON10 ± 14
W (E9 6)E1 (E10 69)IG SW ON2.0 or lessW (E9 ± 6)± E1 (E10 ± 69)Idle10 ± 14
OD1 (E9 ± 12)±E1 (E10 ± 69)IG SW ON4.0 ± 6.0
A/C (E9 34)E1 (E10 69)A/C SW ON (at idle)2.0 or lessA/C (E9 ± 34)± E1 (E10 ± 69)A/C SW OFF10 ± 14
ACMG (E9 23)E1 (E10 69)A/C SW ON (at idle)2.0 or lessACMG (E9 ± 23)± E1 (E10 ± 69)A/C SW OFF10 ± 14
TR (E9 ± 37)±E1 (E10 ± 69)IG SW ON10 ± 14
VT01 (E9 ± 40)E2 (E10 65)IG SW ONThrottle (or sub±throttle) valve fully closed1.0 or less
VT02 (E9 ± 39)± E2 (E10 ± 65)IG SW ONThrottle (or sub±throttle) valve fully open3.0 ± 5.5
NEO (E9 ± 38)±E1 ± (E10 ± 69)IG SW ON4.0 ± 6.0
Engine & ECT ECU Terminals
FI±132EFI SYSTEM ± Electronic Control System (Engine & ECT ECU)
WhereEverybodyKnowsYourName

B. Inspect resistance of engine & ECT ECU wiring connectorsNOTICE: Do not touch the ECU terminals.
Check the resistance between each terminal of the wiring
connectors.w Disconnect the SST (check harness) connectors
from the ECU.
w Measure the resistance at each terminal.
FI±133EFI 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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wDisconnect the SST from the wiring connectors.
SST 09990±01000
4. REINSTALL ENGINE & ECT ECU TO FLOOR PANEL
(a) Connect the two ECU connectors.w Match the male connector correctly with the female
connector, then press them together.
w Tighten the bolt.
Make sure the connector is completely connected, by tight-
ening the bolt until there is a clearance of less than 1 mm
(0.04 in.) between bottom of the male connector and end of
the female connector.
(b) Install the ECU with the bolt.
(c) Install the ECU protector with the two nuts.
(d) Install the floor carpet.
(e) Install the instrument panel under cover with the two clips.
5. RECONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY FI±135
EFI SYSTEM
± Electronic Control System (Engine & ECT ECU)
WhereEverybodyKnowsYourName

Fuel Cut RPM
INSPECTION OF FUEL CUT RPM
1. WARM UP ENGINEAllow the engine to warm up to normal operating
temperature.
2. CONNECT TACHOMETER Connect the test probe of a tachometer to terminal IG of the
check connector.
NOTICE
w Never allow the tachometer terminal to touch ground as
it could result in damage to the igniter and/or ignition
coil.
w As some tachometers are not compatible with this
ignition system, we recommend that you confirm the
compatibility of yours before use.
3. INSPECT FUEL CUT OPERATION
(a) Increase the engine speed to at least 2,500 rpm.
(b) Check for injector operating noise.
(c) Check that when the throttle lever is released, injectoroperation noise stops momentarily and then resumes.
HINT:
w The vehicle should be stopped.
w Measure with the A/C OFF.
Fuel return rpm: 1,400 rpm
4. REMOVE TACHOMETER
FI±136
± Electronic Control System (Fuel \
Cut RPM)EFI SYSTEM
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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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