2000 LEXUS GS400 ABS

F06049
F02821
Hydraulic Brake
BoosterSub±Wire harness S (SST)
FRONT
REAR
AIR BLEEDActuator Checker (SST)
± BRAKEHYDRAULIC BRAKE BOOSTER
BR±43
2151 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
3. IN CASE OF USING ABS ACTUATOR CHECKER:
INSPECT HYDRAULIC BRAKE BOOSTER OPERA-
TION
(a) Inspect the battery positive voltage.
Battery positive voltage: 10 ± 14 V
(b) Disconnect the 2 connectors from hydraulic brake boost-
er.
(c) Connect the actuator checker (SST) to the hydraulic
brake booster side wire harness via the sub±wire harness
S (SST), as shown in the chart below.
SST 09990±00150, 09990±00480
HINT:
Connect the connector with the label of ºFRONTº attached to
the connector of actuator checker.
(d) Connect the red cable of the checker to the battery posi-
tive (+) terminal and the black cable to the negative (±) ter-
minal.
(e) Place ºSHEET Gº (SST) of ºFRONTº on actuator checker.
SST 09990±00240
(f) Turn the ignition switch OFF, depress the brake pedal
more than 40 times.
(g) Check that the brake pedal becomes heavy to depress.
If the pedal does not become to be heavy to depress, check and
replace the brake line and hydraulic brake booster.
(h) Turn the ignition switch ON, check the pump motor opera-
tion noise.
If the pump motor does not operate, check and replace the wire
harness and pump motor.

F04706
F02828
F02827
BR±44
± BRAKEHYDRAULIC BRAKE BOOSTER
2152 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
(i) Inspect the front TRAC & VSC solenoid operation.
(1) Push in and hold the ºSA1º and ºSA2º switches si-
multaneously, depress strongly and hold the brake
pedal with stable force.
NOTICE:
Do not keep the ºSA1º and ºSA2º pushed down for more
than 10 seconds. When operating it continuously, set the
interval of more than 20 seconds.
(2) Check that the brake pedal cannot be depressed.
If the pedal can be depressed, replace the hydraulic brake
booster.
(3) Release the ºSA1º switch and check that the brake
pedal can be depressed.
If the pedal cannot be depressed, replace the hydraulic brake
booster.
(4) Release the ºSA2º switch and check that the brake
pedal can be depressed.
If the pedal cannot be depressed, replace the hydraulic brake
booster.
(j) Inspect the right front ABS solenoid operation.
(1) Turn the selector switch to ºRHº position.
(2) Push and hold in the MAIN push switch and ºSA2º
switch simultaneously, depress and hold the brake
pedal with stable force.
NOTICE:
Do not keep the MAIN push switch and ºSA2º switch
pushed down for more than 10 seconds. When operating
it continuously, set the interval of more than 20 seconds.
(3) Check that the brake pedal cannot be depressed.
If the pedal can be depressed, replace the hydraulic brake
booster.
(4) Release the MAIN push switch and ºSA2º switch si-
multaneously and check that the brake pedal can
be depressed.
If the pedal cannot be depressed, replace the hydraulic brake
booster.
(5) Release the brake pedal.
(6) Depress and hold the brake pedal with stable force,
push and hold in MAIN push switch.
NOTICE:
Do not keep the MAIN push switch pushed down for more
than 10 seconds. When operating it continuously, set the
interval of more than 20 seconds.
(7) Check that the brake pedal cannot be depressed.
If the pedal can be depressed, replace the hydraulic brake
booster.

F04707
F02829
± BRAKEHYDRAULIC BRAKE BOOSTER
BR±45
2153 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
(8) Release the MAIN push switch, and check that the
brake pedal can be depressed.
If the pedal cannot be depressed, replace the hydraulic brake
booster.
(9) Release the brake pedal.
(k) Inspect the left front ABS solenoid operation.
(1) Turn the selector switch to ºLHº position.
(2) Push and hold in the MAIN push switch and ºSA1º
switch simultaneously, depress and hold the brake
pedal with stable force.
NOTICE:
Do not keep the MAIN push switch and ºSA1º switch
pushed down for more than 10 seconds. When operating
it continuously, set the interval of more than 20 seconds.
(3) Check that the brake pedal cannot be depressed.
If the pedal can be depressed, replace the hydraulic brake
booster.
(4) Release the MAIN push switch and ºSA1º switch si-
multaneously, and check that the brake pedal can
be depressed.
If the pedal cannot be depressed, replace the hydraulic brake
booster.
(5) Release the brake pedal.
(6) Depress and hold the brake pedal with stable force,
push and hold in MAIN push switch.
NOTICE:
Do not keep the MAIN push switch pushed down for more
than 10 seconds. When operating it continuously, set the
interval of more than 20 seconds.
(7) Check that the brake pedal cannot be depressed.
If the pedal can be depressed, replace the hydraulic brake
booster.
(8) Release the MAIN push switch, and check that the
brake pedal can be depressed.
If the pedal cannot be depressed, replace the hydraulic brake
booster.
(9) Release the brake pedal.
(l) Turn the ignition switch OFF, then reconnect the connec-
tor of sub±wire harness from the one with label of
ºFRONTº to ºREARº.
(m) Place ºSHEET Gº of ºREARº on the actuator checker.
(n) Jack up and support the vehicle.
(o) Start the engine and run it at idle.

F02830
F02831
BR±46
± BRAKEHYDRAULIC BRAKE BOOSTER
2154 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
(p) Inspect the rear TRAC & VSC solenoid.
(1) Release the parking brake pedal and shift the shift
lever to ºLº position.
(2) Push and hold the ºSA3º switch and ºSTRº switch
simultaneously.
NOTICE:

Do not keep the ºSTRº switch pushed down for more
than 10 seconds.

Do not keep the ºSA3º switch pushed down for more
than 5 seconds.

When operating it continuously, set the interval of
more than 20 seconds.
(3) Check that the rear wheels stop.
If the rear wheels rotate, replace the hydraulic brake booster.
(4) Release the ºSA3º switch and ºSTRº switch simulta-
neously.
(5) Check that the rear wheels rotate.
If the rear wheels stop, replace the hydraulic brake booster.
(q) Inspect the right rear ABS solenoid.
(1) Turn the selector switch to ºRHº position.
(2) Depress the brake pedal several times and release
the brake pedal when the pump begins rotating.
Wait until the pump stops.
(3) Turn the ignition switch OFF.
(4) Depress the brake pedal with a force of 343 N (35
kgf, 77 lbf), record the fluid surface in the reservoir
tank of the hydraulic brake booster.
(5) Press the MAIN push switch for 10 sec., and check
that the fluid surface in the reservoir tank of the hy-
draulic brake booster does not rise up at this time.
If the fluid surface level rises up, replace the hydraulic brake
booster.
NOTICE:
Do not press MAIN push switch for more than 10 sec. When
operating the switch continuously, do it an interval of more
than 20 seconds.
(6) Start the engine and run it at idle.
(7) Depress the brake pedal.
(8) Release the parking brake pedal and shift the shift
lever to ºLº position.
(9) Once, release the brake pedal. After depressing the
brake pedal with stable force, then push and hold
MAIN push switch.
(10) Check that the right rear wheel rotates.
If the right rear wheel stops, replace the hydraulic brake boost-
er.

F02832
± BRAKEHYDRAULIC BRAKE BOOSTER
BR±47
2155 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
(r) Inspect the left rear ABS solenoid.
(1) Turn the selector switch to ºLHº position.
(2) Depress the brake pedal several times and release
the brake pedal when the pump begins rotating.
Wait until the pump stops.
(3) Turn the ignition switch OFF.
(4) Depress the brake pedal with a force of 343 N (35
kgf, 77 lbf), record the fluid surface in the reservoir
tank of the hydraulic brake booster.
(5) Press the MAIN push switch for 10 sec., and check
that the fluid surface in the reservoir tank of the hy-
draulic brake booster does not rise up at this time.
If the fluid surface level rises up, replace the hydraulic brake
booster.
NOTICE:
Do not press MAIN push switch for more than 10 sec. When
operating the switch continuously, do it an interval of more
than 20 seconds.
(6) Start the engine and run it at idle.
(7) Depress the brake pedal.
(8) Release the parking brake pedal and shift the shift
lever to ºLº position.
(9) Once, release the brake pedal. After depressing the
brake pedal with stable force, then push and hold
MAIN push switch.
(10) Check that the left rear wheel rotates.
If the left rear wheel stops, replace the hydraulic brake booster.
(s) Stop the engine and lower the vehicle.
(t) Remove the ºSHEET Gº (SST) and disconnect the actua-
tor checker (SST) and sub±wire harness S (SST) from the
hydraulic brake booster.
(u) Connect the 2 connectors to the actuator.
(v) Clear the DTC (See page DI±389).

F06049
± BRAKEBRAKE FLUID
BR±5
2113 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
(g) Bleed right front brake line.
(1) Select ºFR LINEº on the LEXUS hand±held tester.
(2) With ºFR LINEº turned ON with the LEXUS hand±
held tester, depress the brake pedal and hold it to
bleed the right front brake caliper.
(3) Repeat step (2) until there are no more air bubbles
in the fluid.
(h) Bleed left front brake line.
(1) Select ºFL LINEº on the LEXUS hand±held tester.
(2) With ºFL LINEº turned ON with the LEXUS hand±
held tester, depress the brake pedal and hold it to
bleed the left front brake caliper.
(3) Repeat step (2) until there are no more air bubbles
in the fluid.
(i) Bleed rear brake line.
(1) Select ºRR LINEº on the LEXUS hand±held tester.
(2) With ºRR LINEº turned ON with the LEXUS hand±
held tester, bleed the left and right rear brake cali-
per.
(j) Disconnect the LEXUS hand±held tester from DLC3.
(k) Clear the DTC (See page DI±389).
3. IN CASE OF USING ABS ACTUATOR CHECKER
(SST):
BLEED HYDRAULIC BRAKE BOOSTER
HINT:
If the hydraulic brake booster has been disassembled, discon-
nect the brake line from the hydraulic brake booster or if the res-
ervoir becomes empty, bleed the hydraulic brake booster.
(a) Disconnect the 2 connectors from the hydraulic brake
booster.

± INTRODUCTIONFOR ALL OF VEHICLES
IN±17
17 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
2. FOR VEHICLES EQUIPPED WITH A CATALYTIC CONVERTER
CAUTION:
If large amount of unburned gasoline flows into the converter, it may overheat and create a fire haz-
ard. To prevent this, observe the following precautions and explain them to your customer.
(a) Use only unleaded gasoline.
(b) Avoid prolonged idling.
Avoid running the engine at idle speed for more than 20 minutes.
(c) Avoid spark jump test.
(1) Perform spark jump test only when absolutely necessary. Perform this test as rapidly as possible.
(2) While testing, never race the engine.
(d) Avoid prolonged engine compression measurement.
Engine compression tests must be done as rapidly as possible.
(e) Do not run engine when fuel tank is nearly empty.
This may cause the engine to misfire and create an extra load on the converter.
(f) Avoid coasting with ignition turned off.
(g) Do not dispose of used catalyst along with parts contaminated with gasoline or oil.
3. IF VEHICLE IS EQUIPPED WITH MOBILE COMMUNICATION SYSTEM
For vehicles with mobile communication systems such as two±way radios and cellular telephones, observe
the following precautions.
(1) Install the antenna as far as possible away from the ECU and sensors of the vehicle's electronic
system.
(2) Install the antenna feeder at least 20 cm (7.87 in.) away from the ECU and sensors of the ve-
hicle's electronic systems. For details about ECU and sensors locations, refer to the section on
the applicable component.
(3) Avoid winding the antenna feeder together with other wiring as much as possible, and also avoid
running the antenna feeder parallel with other wire harnesses.
(4) Check that the antenna and feeder are correctly adjusted.
(5) Do not install powerful mobile communications system.
4. FOR USING OBD II SCAN TOOL OR LEXUS HAND±HELD TESTER
CAUTION:
Observe the following items for safety reasons:

Before using the OBD II scan tool or LEXUS hand±held tester, the OBD II scan tool's instruction
book or LEXUS hand±held tester's operator manual should be read thoroughly.

Be sure to route all cables securely when driving with the OBD II scan tool or LEXUS hand±held
tester connected to the vehicle. (i.e. Keep cables away from feet, pedals, steering wheel and
shift lever.)

Two persons are required when test driving with the OBD II scan tool or LEXUS hand±held tes-
ter, one person to drive the vehicle and the other person to operate the OBD II scan tool or LEX-
US hand±held tester.

IN04S±10
IN±20± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
20 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
GENERAL INFORMATION
A large number of ECU controlled systems are used in the LEXUS GS400/GS300. In general, the ECU con-
trolled system is considered to be a very intricate system requiring a high level of technical knowledge and
expert skill to troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, trouble-
shooting of these systems is not complex. If you have adequate understanding of the system and a basic
knowledge of electricity, accurate diagnosis and necessary repair can be performed to locate and fix the
problem. This manual is designed through emphasis of the above standpoint to help service technicians
perform accurate and effective troubleshooting, and is compiled for the following major ECU controlled sys-
tems:
The troubleshooting procedure and how to make use of it are described on the following pages.
SystemPage
1. Engine 2JZ ± GEDI±1
2. Engine 1UZ ± FEDI±156
3. Automatic TransmissionDI±316
4. ABS & Hydraulic Brake Booster Power Supply SystemDI±387
5. Vehicle Skid Control (VSC) & Brake Assist (BA) SystemDI±473
6. Power Tilt and Power Telescopic Steering ColumnDI±517
7. Supplemental Restraint SystemDI±550
8. Power Seat Control SystemDI±683
9. Cruise Control SystemDI±704
10.Engine Immobiliser SystemDI±726
11. Combination Meter SystemDI±744
12.Sliding Roof SystemDI±764
13.Body No. 1 Control SystemDI±776
14.Body No. 2 Control SystemDI±820
15.Driver Door Control SystemDI±856
16.Passenger Door Control SystemDI±889
17.Rear Left Door Control SystemDI±921
18.Rear Right Door Control SystemDI±938
19.Multiplex Communication SystemDI±955
20.LEXUS Navigation SystemDI±1022
21.Air Conditioning SystemDI±1059
FOR USING OBDII SCAN TOOL OR LEXUS HAND±HELD TESTER

Before using the scan tool or tester, the scan tool's instruction book or tester's operator manual should
be read thoroughly.

If the scan tool or tester cannot communicate with ECU controlled systems when you have connected
the cable of the scan tool or tester to DLC3, turned the ignition switch ON and operated the scan tool,
there is a problem on the vehicle side or tool side.
(1) If communication is normal when the tool is connected to another vehicle, inspect the diagnosis
data link line (Bus
line) or ECU power circuit of the vehicle.
(2) If communication is still not possible when the tool is connected to another vehicle, the problem
is probably in the tool itself, so perform the Self Test procedures outline in the Tester Operator's
Manual.