Lexus RX300 (MCU15). Service manual - part 240

D10072

Engine & ECT ECU

Pattern Select 
Switch

J/B No. 3

MPX2

E9

18

W–R

11

B5

MPX1

SNOW

B8

15

Y–B

3

4

W–B

3D

3H

8

9

IH

W–B

Body ECU

DI–192

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

LEXUS RX300   (RM785E)

Pattern Select Switch Circuit

CIRCUIT DESCRIPTION

When 2nd start mode is selected with the pattern select switch, the Engine & ECT ECU controls the solenoid
valves and the transmission starts from 2nd gear.
In D range, the transmission automatically shifts up through 3rd to O/D as usual.
In 2nd range, the transmission is held in 2nd gear.

WIRING DIAGRAM

DI84L–01

D10073

4

3

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

DI–193

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Check pattern select switch.

PREPARATION:
Disconnect the pattern select switch connector.
CHECK:
Check continuity between terminals 1 and 2 of pattern select
switch connector when the select switch is set to SNOW posi-
tions.
OK:

Switch condition

Tester connection

Specified condition

SNOW

3 – 4

Continuity

If the continuity is not as specified, replace the switch.

Q00758

Engine & ECT ECU

+B

OD1

E10

24

Y–G

C16

14

OD

Cruise Conrol ECU

DI–194

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

LEXUS RX300   (RM785E)

O/D Cancel Signal Circuit

CIRCUIT DESCRIPTION

While driving uphill with cruise control activated, in order to minimize gear shifting and provide smooth cruis-
ing overdrive may be prohibited temporarily under some condition.
The cruise control Engine & ECT ECU sends O/D cut signals to the Engine & ECT ECU as necessary and
the Engine & ECT ECU cancels overdrive shifting until these signals are discontinued.

WIRING DIAGRAM

DI0D0–07

D00835

ON

OD1

(+)

(–)

AB0119

N19917

I00742

ON

O/D

(+)

(–)

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

DI–195

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Check voltage between terminal OD1 of Engine & ECT ECU and body ground.

PREPARATION:
Turn the ignition switch ON.
CHECK:
Measure voltage between terminal OD1 of Engine & ECT ECU
and body ground.
OK:

Voltage: 10 – 14 V

OK

Proceed to next circuit inspection shown on
matrix chart (See page DI–160).

NG

2

Check voltage between terminal OD of cruise control ECU harness side connec-
tor and body ground.

PREPARATION:
(a)

Disconnect the cruise control ECU connector.

(b)

Turn the ignition switch ON.

CHECK:
Measure voltage between terminal OD of cruise control ECU
harness side connector and body ground.
OK:

Voltage: 10 – 14 V

OK

Check and replace the cruise control ECU.

NG