Lexus RX300 (MCU15). Service manual - part 365

I19183

MPX2

MPX1

MPX2

MPX1

Driver Door

Theft Deterrent

”T5”

DI–690

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Check driver door ECU.

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

NG

Replace the driver ECU.

OK

2

Check wireharness.

PREPARATION:
Disconnect connector of ”T5” of theft deterrent ECU and driver
door ECU and ”R11” of rear left door ECU.
CHECK:
(a)

Check continuity between terminals MPX2 of theft deter-
rent ECU and MPX1 of driver door ECU.

(b)

Check continuity between terminals MPX2 of driver door
ECU and MPX1 of rear left door ECU.

OK:
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 driver door ECU.

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–691

LEXUS RX300   (RM785E)

DTC

B1212 / 12

Front passenger door ECU commu-
nication stop

CIRCUIT DESCRIPTION

This DTC is output when communication stops between front passenger door ECU and body ECU.

DTC No.

DTC Detecting Condition

Trouble Area

B1212/12

No communication from front passenger door ECU more than

S Front passenger door ECU

B1212/12

No communication from front  assenger door ECU more than

10 seconds.

Front  assenger door ECU

S Wireharness

WIRING DIAGRAM

See page DI–688

INSPECTION PROCEDURE

1

Check front passenger door ECU.

CHECK:
Check if the front passenger door window glass auto up.
HINT:
With this inspection, the front passenger door ECU CPU can be diagnosed if it works normally or not.

NG

Replace the front passenger door ECU.

OK

DI2B0–09

I07386

MPX2

MPX2

MPX1

MPX1

E8

DI–692

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

LEXUS RX300   (RM785E)

2

Check wireharness

PREPARATION:
Disconnect connector ”E8” of engine & ECT ECU and ”R13” of
rear right door ECU.
CHECK:
(a)

Check continuity between terminals MPX1 of engine &
ECT ECU and MPX2 of passenger door ECU.

(b)

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

OK:
There is a continuity in wireharness of both (a) and (b) or (a) 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 passenger door ECU.

I19212

Body ECU

Driver Door
ECU

Sliding Roof
ECU

Engine & ECT ECU

Passenger Door
Door

Rear Right Door
ECU

Center Cluster
Integration Panel

Rear Left
Door ECU

A/C and Combination
Meter Integrated
ECU

Theft Deterrent
ECU

Double Lock 
Control Relay

+B Short

GND Short

Example:

Example:

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DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–693

LEXUS RX300   (RM785E)

DTC

B1214 / 14

System communication bus malfunc-
tion (+B short)

DTC

B1215 / 15

System communication bus malfunc-
tion (GND short)

CIRCUIT DESCRIPTION

This DTC is output when +B or GND short occurs on door system communication bus. If +B or GND short
is detected on door system communication bus, separate it by bus cut relay in body ECU to prevent while
communication buses’ failure.

WIRING DIAGRAM

See page DI–688.

DI84Z–01