Lexus SC300 / Lexus SC400. Manual - part 839

Check for open in harness and connector between terminals E01, E02 of engine
(& ECT) ECU connector and body ground (See page 

IN–27

).

Disconnect injector connector (See page 

FI–26

Resistance:  13.4 – 14.2 

Ω

 at 20

°

C (68

°F)

•

Injection volume
70 – 88 cc/15 sec. (4.3 – 5.4 cu in.)
Difference between each injector:
Less than 9 cc (0.5 cu in.)

•

L

e

a

k

a

g

e

Fuel drop:  One drop or less per minute.

Measure resistance of injector.

Check injection volume of injector

(See page 

FI–30

).

Replace injector.

Check and replace engine (& ECT) ECU.

Repair or replace harness or connector.

Check injectors.

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–131

Back Up Power Source Circuit

CIRCUIT DESCRIPTION

Battery voltage is supplied to terminal BATT of the ECU even when the ignition switch is off for use by
the diagnostic code memory and air–fuel ratio adaptive control value memory, etc.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Check for short in all the harness and
components connected to EFI fuse.

Check EFI fuse.

Check of terminal BATT.

Proceed to next circuit inspection shown on
matrix chart (See page 

TR–35

).

Check operation for the back up.

Check and replace ECU.

Check and repair harness or connector
 between battery, EFI fuse and ECU.

WIRING DIAGRAM

TR–130

–

ENGINE TROUBLESHOOTING

Circuit Inspection

OK

NG

OK

NG

YES

NO

INSPECTION PROCEDURE

1

Check EFI fuse.

C

OK

P

Remove EFI fuse from R/B No.2.

Check continuity of EFI fuse.

Continuity

Check for short in all the harness and components con-
nected to EFI fuse (See attached wiring diagram).

2

Check voltage between terminal BATT of engine & ECT ECU connector and body ground.

C

OK

P

Connect the Check Harness A.
(See page 

TR–30

).

Measure voltage between terminal BATT of engine &
ECT ECU connector and body ground.

Voltage:

10 – 14 V

Check and repair harness or connector between engine
& ECT ECU and EFI fuse, EFI fuse and battery.

3

Are the diagnostic codes still in the memory when the ignition switch is turned OFF?

Check and replace engine & ECT ECU.

Proceed to next circuit inspection shown on ma-
trix chart (See page 

TR–35

).

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–131

Injector Circuit

CIRCUIT DESCRIPTION

The injectors are provided to the intake manifold. They inject fuel into the cylinders based on the signals from
the engine & ECT ECU.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Replace ignition relay.

Check voltage between terminals #10 ~ 40 of
engine & ECT ECU and body ground.

Check ignition relay.

Check continuity between terminal E01, E02
and body ground.

Repair or replace harness or
connector.

Repair or replace harness or
connector.

Replace injector.

Check for open in harness and connector
between ignition relay and ECU.

Check operation for injectors.

Proceed to next circuit inspection shown on
matrix chart (See page 

TR–35

).

Check and repair harness and connector
between ignition relay and battery.

TR–132

–

ENGINE TROUBLESHOOTING

Circuit Inspection