Exhaust Heat Recirculation System Circuit [10/2022 - ]: Procedure
WARNING: This page is about a different car, the 2025 Lexus RX 450h+, 2025 Lexus RX 350h, 2024 Lexus RX 450h+, 2024 Lexus RX 350h, and 2023 Lexus RX 350h. However, it is still accessible from the selected car via links, so may be relevant.
- CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - TEMPERATURE SWITCH (FOR EXHAUST HEAT RECIRCULATION SYSTEM) - BODY GROUND)
- Disconnect the Q2 temperature switch (for exhaust heat recirculation system) connector.
- Disconnect the H21 combination meter assembly connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition Q2-2 (TWS2) - H21-38 (TWS2) Always Below 1 Ω Q2-1 (GND) - Body ground Always Below 1 Ω Q2-2 (TWS2) or H21-38 (TWS2) - Body ground Always 10 kΩ or higher Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (TEMPERATURE SWITCH (FOR EXHAUST HEAT RECIRCULATION SYSTEM) - COMBINATION METER ASSEMBLY)
Result:
OK
See step 2
- CHECK COMBINATION METER ASSEMBLY
- Turn the ignition switch to ON.
- Disconnect the Q2 temperature switch (for exhaust heat recirculation system) connector.
- Check the water temperature receiver gauge in the combination meter assembly.
Result
Result Proceed to Water temperature receiver gauge needle jumps from normal value to HI side A Water temperature receiver gauge needle jumps to HI side and stays there even after the connector is disconnected B Water temperature receiver gauge needle does not move from normal value even after the connector is disconnected C
Result:
A
END
Result:
C
REPLACE COMBINATION METER ASSEMBLY. Refer to REMOVAL [10/2022 - 10/2024] , or refer to REMOVAL [10/2024 - ]
Result:
B
See step 3
- REPLACE TEMPERATURE SWITCH (FOR EXHAUST HEAT RECIRCULATION SYSTEM)
- Replace the temperature switch (for exhaust heat recirculation system).
Refer to REMOVAL [10/2022 - 08/2023] , or refer to REMOVAL [08/2023 - ]
Result
Proceed to NEXT
Result:
NEXT
See step 4
- Replace the temperature switch (for exhaust heat recirculation system).
- CHECK COMBINATION METER ASSEMBLY
- Turn the ignition switch to ON.
- Disconnect the Q2 temperature switch (for exhaust heat recirculation system) connector.
- Check the water temperature receiver gauge in the combination meter assembly.
Result
Result Proceed to Water temperature receiver gauge needle jumps from normal value to HI side A Water temperature receiver gauge needle jumps to HI side and stays there even after the connector is disconnected B
Result:
A
END
Result:
B
REPLACE COMBINATION METER ASSEMBLY. Refer to REMOVAL [10/2022 - 10/2024] , or refer to REMOVAL [10/2024 - ]