Lexus RX300 (MCU15). Service manual — part 253

DI–244

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DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

LEXUS RX300 (RM785E)

INSPECTION PROCEDURE

1

Check brake fluid level.

CHECK:
Check the amount of brake fluid in the reservoir.

NG

Check and repair brake fluid leakage and add
fluid.

OK

2

Check brake fluid level warning switch (See page BE–68).

NG

Replace brake fluid level warning switch.

OK

3

Check for open circuit in all the harness and components connected to brake
fluid level warning light (See page IN–32).

NG

Repair or replace harness or connector.

OK

Check and replace skid control ECU.

F02659

ENG–

ENG+

TRC+

TRC–

14

21

20

13

22

14

24

16

R–Y

A22

Engine and ECT ECU

ENG+

ENG–

TRC+

TRC–

Skid Control ECU

E9

E9

E9

E9

A22

A22

A22

BR–W

GR

P–B

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DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

DI–245

LEXUS RX300 (RM785E)

DTC

C1203 / 53

Engine and ECT ECU Communication
Circuit Malfunction

CIRCUIT DESCRIPTION

The circuit is used to send TRC & VSC control information from the skid control ECU to the engine and ECT
ECU (TRC+, TRC–), and engine control information from the engine and ECT ECU to the skid control ECU
(ENG+, ENG–).

DTC No.

DTC Detecting Condition

Trouble Area

C1203 / 53

Either of the following 1., 2. or 3. continues for 5 sec.:

1. When ECU terminal IG1 voltage is 9.5 V or more, the

condition that the data is not transmitted to engine and

ECT ECU continues for more than 5 sec.

2. When ECU terminal IG1 voltage is 9.5 V or more, engine

speed is 500rpm or more and data receipt from engine

and ECT ECU is impossible.

3. The condition that data transmission and reception to/

from engine and ECT ECU become impossible once or

more within 5 sec. repeatedly occurs 10 times.

S TRC+ or TRC– circuit

S ENG+ or ENG– circuit

S Engine and ECT ECU

WIRING DIAGRAM

DI1H0–11

DI–246

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DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

LEXUS RX300 (RM785E)

INSPECTION PROCEDURE

1

Check for open and short circuit in harness and connector between each of ter-
minals ENG+, ENG–, TRC+, TRC– of skid control ECU and engine and ECT ECU
(See page IN–32).

NG

Repair or replace harness or connector.

OK

Check and replace engine and ECT ECU or
skid control ECU.

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DIAGNOSTICS

ABS & BA & TRC & VSC SYSTEM

DI–247

LEXUS RX300 (RM785E)

DTC

C1207 / 37

Neutral Start Switch (Park/Reverse
Range Circuit)

CIRCUIT DESCRIPTION

DTC No.

DTC Detection Condition

Trouble Area

C1207 / 37

When any of the following 1. through 3. is detected:

1. At vehicle speed of 15 km/h (9 mph) or less and when

the condition that open circuit signal of P signal circuit of

neutral start switch is ON continues 5 sec. or more.

2. At vehicle speed of 15 km/h (9 mph) or more, P signal

from neutral start switch is ON, the shift lever position

information from the engine and ECT ECU is other than

in P or N range condition continues for 60 sec. or more.

3. At vehicle speed of 15 km/h (9 mph) or less and when

the condition that open circuit signal of R signal circuit of

neutral start switch is ON continues 2 sec. or more.

S Neutral start switch

S Neutral start switch (Park/Reverse range circuit)

DI1H1–06