1991 LEXUS SC400 wiring

(b) Take out the front side of the floor carpet.
(c) Remove the two nuts and protector.
(d) Remove the nut, and disconnect the engine & ECT ECU
from the floor panel.
3. INSPECT ENGINE & ECT ECU
A. Install SST (check harness) between engine & ECT ECU and wiring connectors
HINT:
wECU connectors are water±proof and are the bolt type.
w For water±proof type connectors, in order to measure
the voltage of ECU terminals and the resistance of
connected parts, connect a check harness (SST
09990±01000) between the ECU and wiring
connectors, then perform the inspection.
w Avoid inserting a tester probe from the other side of
connector as this noticeably reduces the water±proof
ability.
w Disconnect the ECU connectors by fully loosening the
bolt.
(a) Remove the bolt, and disconnect the two ECU
connectors.
NOTICE:
w Do not pull the wiring harness when disconnecting the
connectors.
w When disconnecting the connector, the ECU's back±up
power source is cut off, so the malfunction codes, etc.
recorded in the ECU memory are cancelled.
w Never insert a tester probe or male terminal used for
inspection purposes into the female terminal of the
vehicle wire harness. Otherwise, the female terminal may
be widened, which can reselt in faulty connection.
(b) Connect SST (check harness) between ECU and wiring
connectors.
SST 09990±01000
HINT: SST (check harness) connector terminals are ar-
ranged the same as those of the ECU. FI±129
EFI SYSTEM
± Electronic Control System (Engine & ECT ECU)
WhereEverybodyKnowsYourName

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)
WhereEverybodyKnowsYourName

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)
WhereEverybodyKnowsYourName

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)
WhereEverybodyKnowsYourName

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

SERVICE DATA (Cont'd)
ECU (cont'd)Voltage (cont'd)
TerminalsConditionSTD voltage (V)
SPD ± E1IG SW ONRotate driving wheel slowly.4 or more
TE1
TE2± E1IG SW ON10 ± 14
WE1
IG SW ON2.0 or less
W ± E1Idling10 ± 14
AD ± E1Idling10 ± 14
OD1 ± E1IG SW ON4.0 ± 6.0
A/C E1
A/C SW ON (at idling)2.0 or less
A/C ± E1A/C SW OFF10 ± 14
ACMG E1
A/C SW ON (at idling)2.0 or less
ACMG ± E1A/C SW OFF10 ± 14
TR ± E1IG SW ON10 ± 14
VT01E2IG SW ON
Throttle (or sub±throttle) valve fully closed1.0 or lessVT01
VT02 ± E2IG SW ONIG SW ON Throttle (or sub±throttle) valve fully open3.0 ± 5.5
NE0 ± E1IG SW ON4.0 ± 6.0
Resistance of wiring connector side
TerminalsConditionSTD voltage (

)
±
#10
#20
#30
#40 +B
+B1±13.2 ± 14.2
±
STJ +B
+B1±2 ± 4
±
ISC1
ISC2
ISC3
ISC4 +B
+B1±10 ± 30
±
FPU +B
+B1±37 ± 44
±
EGR1
EGR2
EGR3
EGR4 +B
+B1±19.9 ± 23.4
±
EGR +B
+B1±33 ± 39
FI±140EFI SYSTEM
± Service Specifications
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName