18/07/2026 8:38 am
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Automotive Q&A
Lexus RX450h inverter-cooling warning has little reservoir movement
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A 2013 RX450h logs an inverter-cooling performance fault after low-speed driving. The dedicated reservoir level is correct, but there is almost no visible circulation in Ready mode and pump current is below the service range. The external pump connector has power and ground with no voltage drop.
Can the pump be diagnosed from the low-voltage side, and where should a general technician stop?
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23/08/2026 12:24 pm
Use the model-specific active test to command the inverter coolant pump and verify low-voltage supply, ground, current and reservoir flow. Inspect accessible hoses for kinks and trapped air only through the approved bleed procedure. Low current with full supply and no circulation supports a pump that is not doing work, provided the circuit is not blocked.
Do not open the inverter, orange connectors or high-voltage battery circuit. If the repair or bleed procedure crosses the high-voltage boundary, a qualified hybrid technician must perform isolation and verification.
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24/08/2026 9:46 am
A hybrid-qualified repair confirmed the external low-voltage pump was receiving full supply but had stopped internally. After pump replacement and the specified bleed, reservoir circulation was clear, current was in range and the thermal test passed.