Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Lost Communication with Humidity/Rain Sensor LIN (B1279)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Exterior / Wiper / Washer / Wiper And Washer System / Lost Communication with Humidity/Rain Sensor LIN (B1279)

DESCRIPTION

The main body ECU (multiplex network body ECU) and rain sensor communicate via LIN communication. The main body ECU (multiplex network body ECU) stores this DTC if communication becomes abnormal.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

DTC Output from

B1279

Lost Communication with Humidity/Rain Sensor LIN

When the battery voltage is 9.5 V or more, a communication malfunction between the main body ECU (multiplex network body ECU) and rain sensor is detected for 10 seconds or more.

  • Rain sensor
  • Harness or connector
  • Main body ECU (multiplex network body ECU)

Main body ECU (multiplex network body ECU)

WIRING DIAGRAM

PROCEDURE

1.

CLEAR DTC

(a) Clear the DTCs.

Click here

Body Electrical > Main Body > Clear DTCs
NEXT

2.

CHECK FOR DTC

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

(b) Check for DTCs.

Click here

Body Electrical > Main Body > Trouble Codes

Result

Proceed to

DTC B1278 is not output.

A

DTC B1278 is output.

B

A

USE SIMULATION METHOD TO CHECK

B

3.

CHECK HARNESS AND CONNECTOR (MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) - RAIN SENSOR)

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

(b) Disconnect the U3 rain sensor connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J9-8 (LIN3) - U3-3 (MPX)

Always

Below 1 Ω

J9-8 (LIN3) or U3-3 (MPX) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.

CHECK HARNESS AND CONNECTOR (FRONT WIPER MOTOR AND LINK ASSEMBLY - POWER SOURCE)

(a) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Condition

Specified Condition

U3-4 (SIG) - U3-2 (ES)

Engine switch off

Below 1 V

Engine switch on (IG)

11 to 14 V

NG

GO TO STEP 6

OK

5.

REPLACE RAIN SENSOR

(a) Replace the rain sensor with a new or known good one.

Click here

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

(c) Check for DTCs.

Click here

Body Electrical > Main Body > Trouble Codes

Result

Proceed to

DTC B1279 is not output.

A

DTC B1279 is output.

B

A

END

B

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

6.

INSPECT MAP LIGHT ASSEMBLY

(a) Remove the map light assembly.

Click here

(b) Inspect the map light assembly.

Click here

OK

REPAIR OR REPLACE HARNESS OR CONNECTOR

NG

REPLACE MAP LIGHT ASSEMBLY

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