Headlight ECU RH Communication Stop Mode [10/2022 - ]: Procedure
WARNING: This page is about a different car, the 2025 Lexus RX 350, 2024 Lexus RX 350, and 2023 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.
- CHECK FOR OPEN IN CAN BUS LINES (HEADLIGHT ECU SUB-ASSEMBLY RH BRANCH LINE)
- Disconnect the cable from the negative (-) battery terminal.
- Disconnect the A44 headlight ECU sub-assembly RH connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition A44-24 (CANH) - A44-23 (CANL) Cable disconnected from negative (-) battery terminal 54 to 69 Ω Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (HEADLIGHT ECU SUB-ASSEMBLY RH)
Result:
OK
See step 2
- CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition A44-12 (GND) - Body ground Cable disconnected from negative (-) battery terminal Below 1 Ω - Reconnect the cable to the negative (-) battery terminal.
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition A44-6 (IGR) - Body ground Ignition switch ON 11 to 14 V Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
Result:
OK
See step 3
- Measure the resistance according to the value(s) in the table below.
- CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition A44-13 (ECUB) - Body ground Ignition switch ON 9.5 to 14 V Result
Proceed to OK NG
Result:
OK
REPLACE HEADLIGHT ECU SUB-ASSEMBLY RH. Refer to REMOVAL [10/2022 - ]
Result:
NG
See step 4
- Measure the voltage according to the value(s) in the table below.
- CHECK HARNESS AND CONNECTOR (HEADLIGHT ECU SUB-ASSEMBLY RH - SEMICONDUCTOR POWER INTEGRATION ECU)
- Disconnect the A74 semiconductor power integration ECU connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition A74-2 (L) - A44-13 (ECUB) Cable disconnected from negative (-) battery terminal Below 1 Ω Result
Proceed to OK NG
Result:
OK
REPLACE SEMICONDUCTOR POWER INTEGRATION ECU. Refer to REMOVAL [10/2022 - 08/2023] , or refer to REMOVAL [08/2023 - ]
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR