Lexus RX300 (MCU15). Service manual - part 368

I19219

Rear Right Door ECU

”R15”

MPX2

Double Lock Control
Relay

I19220

MPX2

”R15”

Passenger Door ECU

Rear Right Door ECU

DI–702

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

LEXUS RX300   (RM785E)

17

Check for short circuit between double lock control relay and rear right door
ECU.

PREPARATION:
(a)

Connect the connector of rear left door ECU.

(b)

Disconnect the connector ”R15” of rear right door ECU.

CHECK:
Check continuity between terminal MPX2 of double lock control
relay and body ground.
OK:

No continuity.

CHECK:
Measure voltage between terminal MPX2 of double lock control
relay and body ground.
OK:

No voltage.

OK

Repair or replace the wireharness between
double lock control relay and rear right door
ECU.

NG

18

Check for short circuit between rear right door ECU and passenger door ECU.

PREPARATION:
(a)

Connect the connector of double lock control relay.

(b)

Disconnect the connector of passenger door ECU.

CHECK:
Check continuity between terminal MPX2 of rear right door ECU
and body ground.
OK:

No continuity.

CHECK:
Measure voltage between terminal MPX2 of rear right door
ECU and body ground.
OK:

No voltage.

OK

Repair or replace the wireharness between rear
right door ECU and passenger door ECU.

NG

I19221

MPX2

Engine & ECT ECU

”E8”

I19222

Body ECU

MPX1

Engine & ECT ECU

”B5”

”E8”

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–703

LEXUS RX300   (RM785E)

19

Check for short circuit between passenger door ECU and engine & ECT ECU.

PREPARATION:
(a)

Connect the connector of rear right door ECU.

(b)

Disconnect the connector ”E8” of engine & ECT ECU.

CHECK:
Check continuity between terminal MPX2 of passenger door
ECU and body ground.
OK:

No continuity.

CHECK:
Measure voltage between terminal MPX2 of passenger door
ECU and body ground.
OK:

No voltage.

OK

Repair or replace the wireharness between en-
gine & ECT ECU and passenger door ECU.

NG

20

Check for short circuit between engine & ECT ECU and body ECU.

PREPARATION:
(a)

Connect the connector of passenger door ECU.

(b)

Disconnect the connector ”B5” of body ECU and sliding
roof ECU.

CHECK:
Check continuity between terminal MPX2 of engine & ECT ECU
and body ground.
OK:

No continuity.

CHECK:
Measure voltage between terminal MPX2 of engine & ECT
ECU and body ground.
OK:

No voltage.

OK

Repair or replace the wireharness between en-
gine & ECT ECU and body ECU.

NG

Replace the body ECU.

DI–704

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

LEXUS RX300   (RM785E)

DTC

B1216 / 16

Rear right door ECU communication
stop

CIRCUIT DESCRIPTION

This DTC is output when communication stops between rear right door ECU and body ECU.

DTC No.

DTC Detecting Condition

Trouble Area

B1216/16

No communication from rear rIght door ECU more than 10

S Rear rIght door ECU

B1216/16

No communication from rear rIght door ECU more than 10

seconds.

Rear rIght door ECU

S Wireharness

WIRING DIAGRAM

See page DI–688

INSPECTION PROCEDURE

1

Check rear right door ECU.

CHECK:
Check if the rear right door window glass auto up.
HINT:
With this inspection rear right door ECU CPU can be diagnosed if it works normal or not.

NG

Replace the rear right door ECU.

OK

DI2B3–07

I19223

Passenger Door

Rear Right Door

MPX1

MPX2

”R15”

Double Lock 
Control Relay

Rear Right Door

”R11”

”R15”

MPX2

MPX1

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–705

LEXUS RX300   (RM785E)

2

Check wireharness.

PREPARATION:
Disconnect connector of passenger door ECU, ”R15” of rear
right door ECU and double lock control relay.
CHECK:
(a)

Check continuity between terminals MPX1 of passenger
door ECU and MPX2 of rear right door ECU.

(b)

Check continuity between terminals MPX1 of rear right
door ECU and MPX2 of double lock control relay.

OK:
If there is OPEN in wireharness of either (a), (b) or (c), please
repair it.
There is a continuity in wireharness of both (a) and (b), or either
(a) or (b).
HINT:
If there is OPEN in wireharness of either (a) or (b), please repair
it.

NG

Repair or replace wireharness.

OK

Replace the rear right door ECU.