ECU LEXUS SC300 1991 Service Repair Manual

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)
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
WhereEverybodyKnowsYourName

SERVICE DATA (Cont'd)
ECU (cont'd)Voltage (cont'd)
TerminalsConditionSTD voltage (V)
IGF1E1
IG SW ON1.0 or lessIGF1
IGF2± E1
IdlingPulse generation
G1
G2 G1 (±)
G2 (±)
±IdlingPulse generation
NE ± NE (+)IdlingPulse generation
M±REL ± E1IG SW ON10 ± 14
FPC E1
Cracking, Sudden racing (6,000 rpm)4.2 ± 6.0
FPC ± E1
IdlingPulse generation
DI ± E1Idling7.5 or more
FPU E1
IG SW ON10 ± 14
FPU ± E1
Restarting high temp.2.0 or less
PAG ± E1IG SW ON10 ± 14
ISC1
ISC2
ISC3
ISC4 ± E1
IG SW ON10 ± 14
VF1
VF2
± E1Maintain engine speed at 2,500 rpm for 120 seconds
after warming up then return to idling.1.0 ± 4.0
OXR1
OXL1 ± E1Maintain engine speed at 2,500 rpm for 120 seconds
after warming upPulse generation
(0 ± 1.0)
HTR1
HTR2 E01IG SW ON10 ± 14HTR2
HTL1
HTL2±
E01
E02Idling2.0 or less
EGR1
EGR2
EGR3
EGR4 ± E1
IG SW ON10 ± 14
EGR ± E1Idling10 ± 14
KNK1
KNK2
± E1IdlingPulse generation
NSW E1IG SW ON
Shift position ºPº or ºNº range1.0 or less
NSW ± E1IG SW ON
Ex. shift position ºPº or ºNº range10 ± 14
FI±139EFI SYSTEM
± Service Specifications
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

DESCRIPTION
The ECU is programmed with data for optimum ignition timing under any and a\
ll operating conditions. Using
data provided by sensors which monitor various engine functions (rpm, i\
ntake air volume, engine temperature,
etc.) the microcomputer (ECU) triggers the spark at precisely the right ins\
tant.
The ECU monitors the engine condition by signals from each sensor, calculates the ignition timing and sends
an ignition signal to the igniter. High voltage from the ignition is distributed to each spark plug in th\
e appropriate
order to generate a spark between the electrodes, which ignites the air±fu\
el mixture.
IGNITERS The igniter temporarily interrupts the primary current with the ignition si\
gnal (IGT signal) from the ECU and
generates sparks at the spark plug. Also, as a fail±safe measure, when ignitio\
n occurs, an ignition confirmation
signal (IGF signal) is sent to the ECU.
IGNITION COIL
The ignition coil uses a closed core coil with the primary coil wrapped \
around the core and the secondary
coil wrapped around the primary coil. This allows the generation of a hi\
gh voltage sufficient to cause a spark
to jump across the spark plug gap.
DISTRIBUTORS
This correctly distributes high voltage to the spark plug of each cylind\
er in the specified ignition order.
ENGINE SPEED SENSOR The engine speed sensor detects the crank angle.
CAM POSITION SENSORS The RH and LH cam position sensors detect the cam angle.
IG±2
±
IGNITION SYSTEM Description
WhereEverybodyKnowsYourName

SYSTEM CIRCUIT
OPERATION
To maintain the most appropriate ignition timing, the ECU sends a control \
signal so that the igniter sends
current to the ignition coil and the spark plugs produce a spark. IG±4
±
IGNITION SYSTEM System Circuit, Operation
WhereEverybodyKnowsYourName