Lexus SC300 / Lexus SC400. Service manual — part 497

B.

Inspect voltage of engine & ECT ECU
Check the voltage between each terminal.

•

Turn the ignition switch ON.

•

Measure the voltage at each terminal.

HINT:

•

Perform all voltage measurements with the connectors
connected.

•

Verify that the battery voltage is 11 V or more when the
ignition switch is ON.

FI–130

EFI SYSTEM – Electronic Control System (Engine & ECT ECU)

Voltage at Engine (& ECT) ECU Wiring Connectors

Terminals

Condition

STD voltage (V)

BATT (E9 – 33) – E1 (E10 – 69)

–

10 – 14

IGSW (E9 – 1)

+B (E9 – 31) – E1 (E10 – 69)

IG SW ON

10 – 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 closed

1.0 or less

IDL2 (E10 – 63)

– E2 (E10 – 65)

IG SW ON

Throttle (or sub–throttle) valve fully open

10 – 14

VTA1 (E10 – 43)

E2 (E10

65)

Throttle (or sub–throttle) valve fully closed

0.1 – 1.0

VTA1 (E10 – 42)

– E2 (E10 – 65)

Throttle (or sub–throttle) valve fully open

3.0 – 6.0

KS (E10 – 66)

– E1 (E10 – 69)

Idling

Pulse generation

THA (E10 – 45)

– E2 (E10 – 65)

Idling

Intake air temp. 20

°

C (68

°

F)

1.0 – 3.0

THW (E10 – 44)

– E2 (E10 – 65)

Idling

Engine Coolant temp. 80

°

C (176

°

F)

0.1 – 1.0

STA (E10 – 77)

– E1 (E10 – 69)

Cranking

6.0 or more

#10 (E10 – 20)

#20 (E10 – 19)

E01 (E10 – 80)

IG SW ON

10 – 14

#30 (E10 – 18)

–

E02 (E10 – 79)

#40 (E10 – 17)

Idling

Pulse generation

IGT1 (E10 – 57)

E1 (E10

69)

Idling

Pulse generation

IGT2 (E10 – 56)

– E1 (E10 – 69)

Idling

Pulse generation

IGF1 (E10 – 58)

E1 (E10

69)

Idling

Pulse generation

IGF2 (E10 – 59)

– E1 (E10 – 69)

Idling

Pulse generation

G1 (E10 – 26)

G1

– (E10–6)

Idling

Pulse generation

G2 (E10 – 25)

–

G2

– (E10–5)

Idling

Pulse generation

NE (E10 – 27)

– G – (E10 – 7)

Idling

Pulse generation

M – REL (E9 – 24)

– E1 (E10 – 69)

IG SW ON

10 – 14

FPC (E9

22)

E1 (E10

69)

Cranking, Sudden racing (6,000 rpm)

4.2 – 6.0

FPC (E9 – 22)

– E1 (E10 – 69)

Idling

Pulse generation

D1 (E9 – 21)

– E1 (E10 – 69)

Idling

7.5 or more

FPU (E10

73)

E1 (E10

69)

IG SW ON

10 – 14

FPU (E10 – 73)

– E1 (E10 – 69)

Restarting high temp.

2.0 or less

PAG (E10 – 74)

– E01 (E10 – 69)

IG SW ON

10 – 14

Engine & ECT ECU Terminals

FI–131

EFI SYSTEM – Electronic Control System (Engine & ECT ECU)

Voltage at Engine (& ECT) ECU Wiring Connectors (Cont’d)

Terminals

Condition

STD voltage (V)

ISC1 (E10 – 35)

ISC2 (E10 – 34)

E1 (E10

69)

IG SW ON

10

14

ISC3 (E10 – 33)

– E1 (E10 – 69)

IG SW ON

10 – 14

ISC4 (E10 – 32)

VF1 (E10 – 29)

E1 (E10

69)

Maintain engine speed at 2,500 rpm for 120 seconds

1 0

4 0

VF2 (E10 – 28)

– E1 (E10 – 69)

Maintain engine s eed at 2,500 r m for 120 seconds
after warming up then return to idling

1.0 – 4.0

OX1 (E10 – 48)

E1 (E10

69)

Maintain engine speed at 2,500 rpm for 120 seconds

Pulse generation

OX2 (E10 – 47)

– E1 (E10 – 69)

Maintain engine s eed at 2,500 r m for 120 seconds
after warming up

Pulse generation

(0 – 1.0)

HT (E10 – 71)

– E01 (E10 – 80)

Idle

2.0 or less

KNK1 (E10 – 50)

E1 (E10

69)

Idle

Pulse generation

KNK2 (E10 – 49)

– E1 (E10 – 69)

Idle

Pulse generation

NSW (E10

76)

E1 (E10

69)

IG SW ON

Shift position “P” or “N” range

1.0 or less

NSW (E10 – 76)

– E1 (E10 – 69)

IG SW ON

Ex. shift position “P” or “N” range

10 – 14

SP1 (E9 – 2)

– E1 (E10 – 69)

IG SW ON

Rotate driving wheel slowly.

4 or more

TE1 (E9 – 20)

E1 (E10

69)

IG SW ON

10

14

TE2 (E9 – 19)

– E1 (E10 – 69)

IG SW ON

10 – 14

W (E9

6)

E1 (E10

69)

IG SW ON

2.0 or less

W (E9 – 6)

– E1 (E10 – 69)

Idle

10 – 14

OD1 (E9 – 12)

– E1 (E10 – 69)

IG SW ON

4.0 – 6.0

A/C (E9

34)

E1 (E10

69)

A/C SW ON (at idle)

2.0 or less

A/C (E9 – 34)

– E1 (E10 – 69)

A/C SW OFF

10 – 14

ACMG (E9

23)

E1 (E10

69)

A/C SW ON (at idle)

2.0 or less

ACMG (E9 – 23)

– E1 (E10 – 69)

A/C SW OFF

10 – 14

TR (E9 – 37)

– E1 (E10 – 69)

IG SW ON

10 – 14

VT01 (E9 – 40)

E2 (E10

65)

IG SW ON

Throttle (or sub–throttle) valve fully closed

1.0 or less

VT02 (E9 – 39)

– E2 (E10 – 65)

IG SW ON

Throttle (or sub–throttle) valve fully open

3.0 – 5.5

NEO (E9 – 38)

– E1 – (E10 – 69) IG SW ON

4.0 – 6.0

Engine & ECT ECU Terminals

FI–132

EFI SYSTEM – Electronic Control System (Engine & ECT ECU)

B.

Inspect resistance of engine & ECT ECU wiring connectors
NOTICE: Do not touch the ECU terminals.
Check the resistance between each terminal of the wiring
connectors.

•

Disconnect the SST (check harness) connectors
from the ECU.

•

Measure the resistance at each terminal.

FI–133

EFI SYSTEM – Electronic Control System (Engine & ECT ECU)