Lexus SC300 / Lexus SC400. Manual - part 883

CIRCUIT DESCRIPTION (Cont’d)

DIAGNOSIS CODE DETECTION DRIVING PATTERN

Purpose of the driving pattern.
(a)  To simulate diag. code detecting condition after diag. code is recorded.
(b)  To check that the malfunction is corrected when the repair is completed confirming that diag. code is no

longer detected.

Initiate test mode (See page 

TR–12

).



Start engine and warm up.



After engine is warmed up, let it idle for 3 min.



With the A/C ON and transmission in D range (O/D OFF), drive at 40–70 mph for 4 min.

HINT: 

If a malfunction exists, the ”CHECK” engine warning light will light up at 1–4 min. of driving at
40–70 mph (64–112 km/h).

NOTICE: 

If the conditions in this test are not strictly followed, detection of the malfunction will
not be possible.

Malfunction: Open in EGR gas temp. sensor circuit

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–109

DIAGNOSTIC CHART

WIRING DIAGRAM

Check voltage of terminal EGR 1 ~ 4.

Check voltage of EGR Step motor power
source.

Check resistance of EGR step motor.

Check for open and short in harness and
connector between EGR step motor and
ECU.

Check and replace ECU.

Check operation for EGR step motor.

Check resistance of EGR gas temp. sensor.

Check for open and short in harness and
connector between EGR gas temp. sensor
and ECU.

Check and replace ECU.

Replace EGR gas temp. sensor.

Replace EGR step motor.

Replace EGR step motor.

Repair or replace harness or
connector.

Repair or replace harness or
connector.

Check for ECU power source
circuit.

TR–110

–

ENGINE TROUBLESHOOTING

NG

OK

OK

NG

INSPECTION PROCEDURE

1

Check voltage between terminals EGR 1 ~ 4 of engine & ECT ECU connector 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 EGR 1 ~ 4 of en-
gine & ECT ECU connector and body ground.

Voltage:

10 – 14 V

Go to step 5.

2

Check voltage between terminals B1 and B2 of EGR step motor connector and body ground.

C

OK

P

(2) Disconnect EGR step motor connector.

(2) Turn ignition switch on.

Measure voltage between terminals B1 and B2 of EGR
step motor connector and body ground.

Voltage:

10 – 14 V

Check for ECU power source circuit 
(See page 

TR–124

).

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–111

OK

NG

OK

NG

OK

NG

3

Check resistance of EGR step motor.

C

OK

P

Disconnect EGR step motor connector.

Measure resistance between terminals shown below.

Replace EGR step motor.

4

Check for open and short in harness and connector between EGR step motor and engine & ECT
ECU (See page 

IN–27

).

Repair or replace harness or connector.

Check and replace engine & ECT ECU.

5

Check operation for EGR step motor.

C

OK

P

Remove EGR step motor.

(2) Connect the battery positive lead to terminals B1

and B2, and the negative lead to terminals S1 – S2
– S3 – S4 in that order.

(2) Connect the battery positive lead to terminals B1

and B2, and the negative lead to terminals S4 – S3
– S2 – S1 in that order.

(2) The valve moves in the closing direction.

(2) The valve moves in the opening direction.

Replace EGR step motor.

TR–112

–

ENGINE TROUBLESHOOTING

Circuit Inspection