1991 LEXUS SC400 engine

WIRING DIAGRAM
DTC44NE Signal Circuit
CIRCUIT DESCRIPTION
The TRAC ECU receives engine speed signals (NE signals) from the ECM.
DTC No.DTC Detecting ConditionTrouble Area
44No signal is input to terminal NEO 0.24 sec. after trac-
tion control is initiated.
Open or short in NEO circuit

ECM

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±198±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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OKNG
OKNG
INSPECTION PROCEDURES
1Check for open and short in harness and connector between terminal NEO of TRA\
C ECU and
terminal NEO of ECM (See page IN±33).
Repair or replace harness or connector.
2Check voltage between terminal NEO of TRAC ECU and body ground.
C
OK
P1. Remove TRAC ECU with connectors still con-
nected.
2. Turn ignition switch on.
Measure voltage between terminal NEO of TRAC ECU
and body ground for the engine conditions below.
Check and replace TRAC ECU or ECM.
If the same code is still output after the diagnostic code is deleted, che\
ck the contact condition of each
connection.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±199
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NOYES
NGOK
OKNG
INSPECTION PROCEDURE
1Is 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.
2Check voltage between terminal VTH of TRAC ECU and body ground.
C
OK
P1. Remove TRAC ECU with connectors still con-
nected.
2. Remove intake air duct.
3. Turn ignition switch on.
Measure voltage between terminal VTH of TRAC ECU
and body ground, when the main throttle valve is turned
from fully closed position to fully opened position by
hand
In addition, as the main throttle valve is turned, the
voltage should increase gradually w ith out interrup-
tion.
Go to step .
3Check for open and short in harness and connector between terminal VTH o\
f TRAC ECU and
terminal VTO1 of ECM (See page IN±33).
Repair or replace harness or connector.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±203
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NOYES
NGOK
OKNG
INSPECTION PROCEDURE
1Is 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.
2Check voltage between terminal VSH or TRAC ECU and body ground.
C
OK
P1. 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 w ith out interrup-
tion.
Go to step
.
3Check 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
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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)
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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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CHECK AND ADJUSTMENT
BR0EC±07
BRAKE PEDAL CHECK AND
ADJUSTMENT
1. CHECK THAT PEDAL HEIGHT IS CORRECT
Pedal height from asphalt sheet:150.4±160.4 mm (5.92±6.31 in.)
If the pedal height is incorrect, adjust it.
2. IF NECESSARY, ADJUST PEDAL HEIGHT
(a) Disconnect the connector from the stop light switch.
(b) Loosen the stop light switch lock nut and remove the stop light switch.
(c) Loosen the push rod lock nut.
(d) Adjust the pedal height by turning the pedal push rod.
(e) Tighten the push rod lock nut.
Torque: 25 N Vm (260 kgf Vcm, 19 ft Vlbf)
(f) Install the stop light switch and turn it until it lightly contacts
the pedal stopper.
(g) Turn the stop light switch back one turn.
(h) Check the clearance (A) between stop light switch and pedal.
Clearance:
0.5±2.4 mm (0.02±0.09 in.)
(i) Tighten the stop light switch lock nut.
(j) Connect the connector to the stop light switch.
(k) Check that the stop lights come on when the brake pedal isdepressed, and go off when the brake pedal is released.
(l) After adjusting the pedal height, check the pedal free±play.
HINT: If clearance (A) between the stop light switch and the
brake pedal stopper has been adjusted correctly, the pedal
freeplay will meet the specifications.
3. CHECK THAT PEDAL FREEPLAY IS CORRECT, AS SHOWN
(a) Stop the engine and depress the brake pedal several times until there is no more vacuum left in the booster.
(b) Push in the pedal by hand until the beginning of the second point of resistance is felt, then measure the distance, as
shown.
Pedal freeplay:
1±6 mm (0.04±0.24 in.)
If incorrect, check the stop light switch clearance. And if the
clearance is OK, then troubleshoot the brake system.
HINT: The freeplay to the first point of resistance is due to the
play between the clevis and pin. It is 1±3 mm (0.04±0.12 in.)
on the pedal.
±
BRAKE SYSTEM CHECK AND ADJUSTMENTBR±7
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4. CHECK THAT PEDAL RESERVE DISTANCE IS CORRECT,
AS SHOWN
Release the parking brake.
With the engine running, depress the pedal and measure the
pedal reserve distance, as shown.
Pedal reserve distance at 490 N (50 kgf, 110.2 lbf):
More than 89 mm (3.50 in.)
If the reserve distance is incorrect, troubleshoot the brake
system.
BRAKE BOOSTER OPERATIONAL TEST
BR03P±0B
1. OPERATING CHECK
(a) Depress the bake pedal several times with the engine off and
check that there is no change in the pedal reserve distance.
(b) Depress the brake pedal and start the engine. If the pedal goes down slightly, operation is normal.
2. AIR TIGHTNESS CHECK
(a) Start the engine and stop it after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes down the
farthest the 1st time, but gradually rises after the 2nd or 3rd
time, the booster is air tight.
(b) Depress the brake pedal while the engine is running, and stop the engine with the pedal depressed. If there is no
change in the pedal reserve travel after holding the pedal for
30 seconds, the booster is air tight.
BRAKE SYSTEM BLEEDING
BR0ED±04
HINT: If any work is done on the brake system or if air in the
brake lines is suspected, bleed the system of air.
NOTICE: Do not let brake fluid remain on painted sur-
faces. Wash it off immediately.
1. REMOVE RESERVOIR CAP Turn the reservoir cap to the ªopenº side and remove it.
2. FILL RESERVOIR WITH BRAKE FLUID
Fluid: SAE J1703 or FMVSS NO.116DOT3
BR±8±
BRAKE SYSTEM CHECK AND ADJUSTMENT
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