Lexus SC300 / Lexus SC400. Service manual - part 240

NO

YES

NG

OK

OK

NG

INSPECTION PROCEDURE

1

Is diagnostic trouble code output for the engine?

Perform diagnostic trouble code check on page 

EG–523

 or 

EG–305

.

Repair circuit indicated by the code output.

2

Check voltage between terminal VSH or TRAC ECU and body ground.

C

OK

P

1.

Remove TRAC ECU with connectors still con-
nected.

2.

Remove intake air duct.

3.

Disconnect step motor connector.

4.

Turn ignition switch on.

Measure voltage between terminal VSH or TRAC ECU
and body ground, when the sub–throttle valve is turned
from fully opened position to fully closed position.

In addition, as the sub–throttle valve is turned, the
voltage should increase gradually with out interrup-
tion.

Go to step 
.

3

Check for open and short in harness and connector between terminal VSH of TRAC ECU and
terminal VTO2 of ECM (See page 

IN–33

).

Repair or replace harness or connector.

–

BRAKE SYSTEM

TRACTION CONTROL SYSTEM (TRAC)

BR–211

NG

OK

NG

OK

4

Check voltage between terminal VTO2 of ECM and body ground with TRAC ECU connector dis-
connected.

C

OK

P

1.

Connect the Check Harness A. (See page 

EG–562

or  

EG–328

).

2.

Disconnect the TRAC ECU connector.

3.

Turn ignition switch on.

Measure voltage between terminal VTO2 of ECM and
body ground, when the sub–throttle valve is fully closed
and fully opened.

Check and replace TRAC ECU.

5

Check voltage of terminal VTA2 of ECM (See page 

EG–608

 or 

EG–388

).

Check and replace ECM.

BR–212

–

BRAKE SYSTEM

TRACTION CONTROL SYSTEM (TRAC)

OK

NG

NG

OK

6

Check for open and short in harness and connector between terminal VTA2 of ECM and sub–
throttle position sensor (See page 

IN–33

)

Repair or replace harness or connector.

Adjust or replace sub–throttle position sensor
(See page 

EG–333

 or 

EG–205

).

7

Check voltage between terminal IDL2 of TRAC ECU and body ground.

C

OK

P

Turn ignition switch on.

Measure voltage between terminal IDL2 or TRAC ECU
connector and body ground, when the sub–throttle
valve is fully closed and fully opened.

Check and replace TRAC ECU.

–

BRAKE SYSTEM

TRACTION CONTROL SYSTEM (TRAC)

BR–213

NG

OK

OK

NG

8

Check voltage between terminal IDL2 of TRAC ECU connector and body ground with TRAC ECU
connector disconnected.

C

OK

Hint

P

1.

Disconnect the TRAC ECU connector.

2.

Turn ignition switch on.

Measure voltage between terminal IDL2 of TRAC ECM
connector and body ground, when the sub–throttle
valve is fully closed and fully opened.

Check and replace TRAC ECU.

9

Check for open and short in harness and connector between terminal IDL2 of TRAC ECU and
ECM (See page  

IN–33

).

Repair or replace harness or connector.

BR–214

–

BRAKE SYSTEM

TRACTION CONTROL SYSTEM (TRAC)