Lexus SC300 / Lexus SC400. Manual - part 686

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

WIRING DIAGRAM

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–133

NG

OK

OK

NG

INSPECTION PROCEDURE

1

Check voltage between terminals #20 ~ 40 of engine & ECT ECU and body ground.

C

OK

P

(2) Connect the Check Harness A.

(See page 

TR–30

)

(2) Turn ignition switch on.

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

Voltage:

10 – 14 V

Go to step 3.

2

Check ignition relay.

C

OK

Hint

P

Remove ignition relay from R/B No.2.

Check continuity between terminals of ignition relay
shown below.

(2) Apply battery voltage between terminals of ignition

relay shown below.

(2) Check continuity between terminals 1 and 2.

Replace ignition relay.

TR–134

–

ENGINE TROUBLESHOOTING

Circuit Inspection

OK

NG

OK

NG

OK

NG

3

Check for open in harness and connector between terminal E01, E02 of engine & ECT ECU con-
nector and body ground (See page 

IN–27

).

Repair or replace harness or connector.

4

Check for open in harness and connector between ignition relay and injector, injector and en-
gine & ECT ECU (See page 

IN–27

).

Repair or replace harness or connector.

5

Check injectors.

C

OK

P

OK

C

Disconnect injector connector (See page 

FI–50

).

Measure resistance of injector.

Resistance:

13.4 – 14.2 

 at 20



C (68



F)

Check injection volume of injector (See page 

FI–52

).

Injection volume
55–70 cc/15 sec. (3.4–4.3 cu in.)
Difference between each injector:
Less than 10 cc (0.6 cu in.)

Leakage
Fuel drop:  Once drop or less per minute.

Replace injector.

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

TR–35

).

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–135