Lexus RX300 (MCU15). Service manual - part 372

DI–718

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

LEXUS RX300   (RM785E)

DTC

B1261 / 61

Engine & ECT ECU communication
stop

CIRCUIT DESCRIPTION

This DTC is output when communication stops between engine & ECT ECU and Body ECU.

DTC No.

DTC Detecting Condition

Trouble Area

B1261/61

No communication from engine & ECT ECU more than 10

S Engine & ECT ECU

B1261/61

No communication from engine & ECT ECU more than 10

seconds.

Engine & ECT ECU

S Wireharness

WIRING DIAGRAM

See page DI–688

INSPECTION PROCEDURE

1

Check engine & ECT ECU.

CHECK:
Check that the engine starts normally.
HINT:
With this inspection, engine & ECT ECU CPU can be diagnosed if it works normally or not.

NG

Replace the engine & ECT ECU.

OK

DI2BB–07

I07400

Body ECU

B5

MPX1

Engine & ECT ECU

E8

MPX2

MPX2

E8

MPX1

Passenger
Door ECU

Engine & ECT ECU

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–719

LEXUS RX300   (RM785E)

2

Check wireharness

PREPARATION:
Disconnect connector ”B5” of body ECU, ”E8” of engine & ECT
ECU and passenger door ECU.
CHECK:
(a)

Check continuity between terminals MPX1 of body No.1
ECU and MPX2 of engine & ECT ECU.

(b)

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

DI–720

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

LEXUS RX300   (RM785E)

DTC

B1269 / 69

Theft deterrent ECU communication
stop

CIRCUIT DESCRIPTION

This DTC is output when communication stops between theft deterrent ECU and body ECU.

DTC No.

DTC Detecting Condition

Trouble Area

B1269/69

No communication from theft deterrent ECU more than 10

S Theft deterrent ECU

B1269/69

No communication from theft deterrent ECU more than 10

seconds.

Theft deterrent ECU

S Wireharness

WIRING DIAGRAM

See page DI–693.

INSPECTION PROCEDURE

1

Check theft deterrent ECU.

CHECK:
Check that the operation of the theft deterrent function is normal.
HINT:
With this inspection, the theft deterrent ECU CPU can be diagnosed if it works normally or not.

NG

Replace the theft deterrent ECU.

OK

DI63C–03

I19227

Theft Deterrent ECU

MPX2

MPX1

MPX1

MPX–

Theft Deterrent ECU

Driver Door ECU

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–721

LEXUS RX300   (RM785E)

2

Check wireharness

PREPARATION:
Disconnect connector of driver door ECU, ”C11” of A/C and
combination meter integrated ECU and ”T5” of theft deterrent
ECU.
CHECK:
(a)

Check continuity between terminals MPX1 of driver door
ECU and MPX2 of theft deterrent ECU.

(b)

Check continuity between terminals MPX1 of theft deter-
rent ECU and MPX– of A/C and combination meter inte-
grated 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 theft deterrent ECU.