Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Interior Light Switch Signal Circuit

DESCRIPTION

The main body ECU (multiplex network body ECU) detects the condition of the door switch and front dome light switch.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Before replacing the main body ECU (multiplex network body ECU), refer to Registration.

Click here

PROCEDURE

1.

READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Main Body / Data List.

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Main Body > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Dome Light DOOR SW

Door switch signal

ON or OFF

ON: Door switch pressed

OFF: Door switch not pressed

-

Dome Light SW

Front dome light switch signal

ON or OFF

ON: Front dome light switch ON

OFF: Front dome light switch OFF

-

Body Electrical > Main Body > Data List

Tester Display

Dome Light DOOR SW

Dome Light SW

OK:

Normal conditions listed above are displayed.

Result

Proceed to

OK

A

Dome Light DOOR SW is not normal

B

Dome Light SW is not normal

C

A

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

GO TO STEP 4

B

2.

INSPECT MAP LIGHT ASSEMBLY

(a) Remove the map light assembly.

Click here

(b) Inspect the map light assembly.

Click here

OK:

Map light assembly is normal.

NG

REPLACE MAP LIGHT ASSEMBLY

OK

3.

CHECK HARNESS AND CONNECTOR (MAP LIGHT ASSEMBLY - MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) AND BODY GROUND)

(a) Disconnect the J9 main body ECU (multiplex network body ECU) connector.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

U12-18 (DOOR) - J9-27 (DMDR)

Always

Below 1 Ω

U12-19 (CILL) - J9-28 (DMON)

Always

Below 1 Ω

U12-20 (GND9) - Body ground

Always

Below 1 Ω

U12-18 (DOOR) or J9-27 (DMDR) - Body ground

Always

10 kΩ or higher

U12-19 (CILL) or J9-28 (DMON) - Body ground

Always

10 kΩ or higher

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.

CHECK HARNESS AND CONNECTOR (MAP LIGHT ASSEMBLY - MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) AND BODY GROUND)

(a) Disconnect the J9 main body ECU (multiplex network body ECU) connector.

(b) Disconnect the U12 map light assembly connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

U12-19 (CILL) - J9-28 (DMON)

Always

Below 1 Ω

U12-20 (GND9) - Body ground

Always

Below 1 Ω

U12-19 (CILL) or J9-28 (DMON) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5.

INSPECT MAP LIGHT ASSEMBLY

(a) Replace the map lamp assembly with a new or known good one.

Click here

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / Main Body / Data List.

(f) Read the Data List according to the display on the Techstream.

Body Electrical > Main Body > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Dome Light SW

Front dome light switch signal

ON or OFF

ON: Front dome light switch ON

OFF: Front dome light switch OFF

-

Body Electrical > Main Body > Data List

Tester Display

Dome Light SW

OK:

Normal conditions listed above are displayed.

Result

Proceed to

Dome Light SW is normal

A

Dome Light SW is not normal

B

A

END (MAP LAMP ASSEMBLY WAS DEFECTIVE)

B

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

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