Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Daytime Running Light Relay Circuit
DESCRIPTION
The main body ECU (multiplex network body ECU) controls the daytime running lights.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
- Inspect the fuses for circuits related to this system before performing the following procedure.
-
Before replacing the main body ECU (multiplex network body ECU), refer to Registration.
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PROCEDURE
| 1. | PERFORM ACTIVE TEST 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 / Active Test.
(e) Perform the Active Test according to the display on the Techstream.
Body Electrical > Main Body > Active Test| Tester Display | Measurement Item | Control Range | Diagnostic Note |
|---|---|---|---|
| Daytime Running Light | Daytime running lights | OFF/ON | This Active Test can only be performed when the customization item DRL function is set to "ON" using the Techstream. |
| Tester Display |
|---|
| Daytime Running Light |
OK:
Daytime running lights illuminate.
| OK | .gif) | PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE |
|
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| 2. | CHECK SEMICONDUCTOR POWER INTEGRATION ECU |
(a) Using a voltmeter, check the signal reading of the semiconductor power integration ECU.
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OK:
Output signal reading is normal.
| NG | | INSPECT SEMICONDUCTOR POWER INTEGRATION ECU (RESULTS OF SIGNAL READING CHECK) |
|
| 3. | CHECK HARNESS AND CONNECTOR (SEMICONDUCTOR POWER INTEGRATION ECU POWER SOURCE AND BODY GROUND) |
| *a | Component without semiconductor power integration ECU connected (Engine Room Relay Block and Junction Block Assembly) | - | - |
(a) Remove the semiconductor power integration ECU from the engine room relay block and junction block assembly.
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(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| B-1 (BATT) - Body ground | Always | 11 to 14 V |
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 1D-14 (GND1) - Body ground | Always | Below 1 Ω |
| 1G-5 (GND2) - Body ground | Always | Below 1 Ω |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 4. | CHECK HARNESS AND CONNECTOR (SEMICONDUCTOR POWER INTEGRATION ECU - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY) |
(a) Disconnect the 2C instrument panel junction block assembly connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 1D-9 (-S) - 2C-28 | Always | Below 1 Ω |
| 1D-9 (-S) or 2C-28 - Body ground | Always | 10 kΩ or higher |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 5. | INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY |
| *a | Component without harness connected (Instrument Panel Junction Block Assembly) | - | - |
(a) Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.
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(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 2C-28 - MB-25 (DRLE) | Always | Below 1 Ω |
| NG | | REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY |
|
| 6. | REPLACE SEMICONDUCTOR POWER INTEGRATION ECU |
(a) Replace the semiconductor power integration ECU with a new one.
Click here
|
| 7. | CHECK OPERATION (DAYTIME RUNNING LIGHTS) |
(a) Check the operation of the daytime running lights.
OK:
Daytime running lights operate normally.
| OK | | END (SEMICONDUCTOR POWER INTEGRATION ECU WAS DEFECTIVE) |
| NG | | REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) |
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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual
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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual
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