Lexus SC300 / Lexus SC400. Manual - part 838

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
connected 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–34

)

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 trouble 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
matrix chart (See page 

TR–39

).

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–127

 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.

 Reference 

INSPECTION USING OSCILLOSCOPE

•

 With the engine idling measure between terminals #10 ~ 60 and E01 of engine (& ECT) ECU.

HINT: The correct waveform appears as shown in the illustration on the below.

DIAGNOSTIC CHART

Check voltage of terminals #10 ~ 60.

Check AM2 and INJ fuses.

Check for open in harness and connector
between ECU and battery.

Check continuity between terminals E01,
E02 and body ground.

Check operation for injectors.

Check and replace ECU.

Check for short in all the harness
and components connected to
AM2 and INJ fuses.

Repair or replace harness or
connector.

Replace injector.

TR–128

–

ENGINE TROUBLESHOOTING

Circuit Inspection

WIRING DIAGRAM

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–129

NG

OK

OK

NG

INSPECTION PROCEDURE

1

Check voltage between terminals #10 



 60 of engine (& ECT) ECU and body ground.

C

OK

P

(2) Connect the Check Harness A. (See page 

TR–34

)

(2) Turn ignition switch on.

Measure voltage between terminals #10 

∼

 

60 of engine

(& ECT) ECU and body ground.

Voltage:  10 – 14 V

Go to step 

.

2

Check AM2 and INK fuses.

C

OK

P

Remove AM2 and INJ fuses from fuse block.

Check continuity of AM2 of INJ fuses.

Continuity

Check for short in all the harness and components
connected to AM2 and INJ fuses.

Check for open in harness and connector between
engine (& ECT) ECU and battery.

TR–130

–

ENGINE TROUBLESHOOTING

Circuit Inspection