Lexus RX300 (MCU15). Service manual - part 260

F06926

E2

PMC

VCM

DI–272

–

DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

HINT:
Start the inspection from step 1 in case of using the hand–held tester and start from step 2 in case of not
using the hand–held tester.

1

Check output value of the master cylinder pressure sensor.

PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch ON, and push the hand–held tester main switch ON.

(c)

Select the DATALIST mode on the hand–held tester.

CHECK:
Check that the brake fluid pressure value of the master cylinder pressure sensor displayed on the hand–held
tester is changing when depressing the brake pedal.
OK:

Brake fluid pressure value must be changing.

OK

Go to step 4.

NG

2

Check master cylinder pressure sensor.

PREPARATION:
Install LSPV gauge to the front brake caliper bleeder plug por-
tion, and bleed air from LSPV gauge.

SST

09709–29018

CHECK:
Start the engine and depress the brake pedal, then check the
relation between the fluid pressure and voltage of PMC and E2
terminals of the master cylinder pressure sensor with connector
still connected.
OK:

Front brake caliper fluid pressure

Voltage

0 kPa (0 Kgf/cm

2

, 0 psi)

0.37 – 0.63 V

5,883 kPa (60 kgf/cm

2

, 853 psi)

1.57 – 1.83 V

11,768 kPa (120 kgf/cm

2

, 1,706 psi)

2.77 – 3.03 V

HINT:
Voltage between terminals VCM and E2: 4.7 – 5.3 V

NG

Replace brake actuator.

OK

–

DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

DI–273

LEXUS RX300   (RM785E)

3

Check for open and short circuit in harness and connector between master cyl-
inder pressure sensor and skid control ECU (See page IN–32).

NG

Repair or replace harness or connector.

OK

4

Check whether or not the ECU terminal STP input voltage is changed when the
stop light switch is turned on and off.

NO

Check stop light switch circuit (See page
BE–53).

YES

Check and replace skid control ECU.

F13430

Instrument Panel J/B

Stop Light
Switch

Skid Control ECU

Light Failure Sensor

Stop
Light RH

J11
Junction 
Connector

Stop
Light LH

J15
Junction 
Connector

J12
Junction 
Connector

J14
Junction 
Connector

High
Mounted 
Stop Light

Fusible
Link Block 
ALT

STOP

W

G–W

A

G–R

W–B

W

G–B

G–Y

G–W

G–Y

G–W

G–R

G–R

G–R

W–B

W–B

G–Y

A

A

A

1

7

STP

BN

A23

1A

1

1E

2

1

3

11

5E

5

5B

5C

9

IA1

1

2

7

3

BC2

3 BD1

3

4

3

4

1

2

BM

BI

5

3

J/B No.5

A

A

W–B

DI–274

–

DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

LEXUS RX300   (RM785E)

DTC

C1249 / 49

Stop Light Switch Circuit

CIRCUIT DESCRIPTION

DTC No.

DTC Detecting Condition

Trouble Area

C1249 / 49

ECU terminal IG1 voltage is 9.5 to 17.2 V and ABS is in

non–operation, the open circuit of stop light switch circuit

continues for 0.3 sec. or more.

Stop light switch circuit

WIRING DIAGRAM

DI1GO–10

F02806

F13605

LOCK

STP

(+)

(–)

–

DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

DI–275

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Check operation of the stop light switch.

CHECK:
Check that the stop light lights up when brake pedal is depressed and turns off when the brake pedal is re-
leased.

OK

Go to step 3.

NG

2

Check stop light circuit (See page BE–53).

NG

Repair or replace stop light circuit.

OK

3

Check voltage between terminal STP of skid control ECU and body ground.

PREPARATION:
Remove the skid control ECU with connectors still connected.
CHECK:
Measure voltage between terminal STP of skid control ECU
and body ground when brake pedal is depressed.
OK:

Voltage: 8 – 14 V

OK

Check and replace skid control ECU.

NG