Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: 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. |
| ○ | Main body ECU (multiplex network body ECU) |
WIRING DIAGRAM
PROCEDURE
| 1. | CLEAR DTC |
(a) Clear the DTCs.
Click here .gif)
|
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| 2. | CHECK FOR DTC |
(a) Turn the engine switch on (IG).
(b) Check for DTCs.
Click here
| Result | Proceed to |
|---|---|
| DTC B1278 is not output. | A |
| DTC B1278 is output. | B |
| A | .gif) | USE SIMULATION METHOD TO CHECK |
|
| 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 |
|
| 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 |
|
| 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
| 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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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual
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