1991 LEXUS SC400 brake

NGOK
NGOK
4Check voltage between terminal VTO2 of ECM and body ground with TRAC ECU connector dis-
connected.
C
OK
P1. 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.
5Check 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)
WhereEverybodyKnowsYourName

OKNG
NGOK
6Check 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 ).
7Check voltage between terminal IDL2 of TRAC ECU and body ground.
C
OK
PTurn 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
WhereEverybodyKnowsYourName

NGOK
OKNG
8Check voltage between terminal IDL2 of TRAC ECU connector and body ground with TRAC ECU
connector disconnected.
C
OK
Hint
P1. 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.
9Check for open and short in harness and connector between terminal IDL2 of TR\
AC ECU and
ECM (See page IN±33).
Repair or replace harness or connector.
BR±214
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

OKNG
10Check sub±throttle position sensor (See page EG±609 or EG±389 ).
Adjust or replace sub±throttle position sensor (See page
EG±333 or EG±205 ).
Check and replace ECM.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±215
WhereEverybodyKnowsYourName

IN±29).
WIRING DIAGRAM
DTC49Engine Communication Circuit
CIRCUIT DESCRIPTION
This circuit is used to send ignition timing retard request signals from the TRAC ECU to\
the ECM in order to retard
the engine ignition timing.
DTC No.DTC Detecting ConditionTrouble Area
49TR2 output voltage differs from TR2 monitorvoltage in
TRAC ECU.
Open or short in TR2 circuit

ECM

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±216±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminal TR2 of TRAC ECU and body ground.
C
OK
Hint
P1. Disconnect TRAC ECU connector.
2. Turn ignition switch on.
Measure voltage between terminal TR2 of TRAC ECU
and body ground.
Voltage: 8 ± 14 V
Check and replace TRAC ECU.
2Check for open and short in harness and connector between TRAC ECU and E\
CM (See page
IN±29).
Repair or replace harness or connector.
Check and replace ECM.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±217
WhereEverybodyKnowsYourName

TR±11
WIRING DIAGRAM
DTC51Engine Malfunction Detection Circuit
CIRCUIT DESCRIPTION
If trouble (trouble which causes the malfunction indicator light to light\
up) occurs in the engine control system,
this circuit senses the trouble and prohibits TRAC control.
DTC No.DTC Detecting ConditionTrouble Area
51
Either of the following (1) and (2) continues formore
than 1 sec.:
(1) Engine speed: 500 RPM or more
(2) Voltage of TRAC ECU terminal TR5: 1 V or less
Short in TR5 circuit

ECM

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±218±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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±MEMO±
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±219
WhereEverybodyKnowsYourName