Why does my Lexus RX 400h say "Check Hybrid System"?

Short answer: On the RX 400h, "Check Hybrid System" plus "Check VSC" with code P0A05 or P0A93 very often means the inverter coolant pump has failed. That small electric pump cools the inverter (the box that powers the hybrid motors). The hybrid system cuts power to protect itself. Owners say the pump is a common, fairly cheap fix. Also check the 12V battery, since a weak one causes odd hybrid warnings.

Symptom: Check Hybrid System and Check VSC warnings, sometimes with power loss or the car shutting down the hybrid system.

What to check first

1. Scan for codes. P0A05 or P0A93 points to the inverter cooling system.
2. Look at the inverter coolant tank with the car on. You should see coolant moving. No movement suggests a dead pump.
3. Test the 12V battery. A weak one causes strange warnings.
4. After a pump replacement, bleed the inverter cooling system using the bleed valve at the inverter radiator.
5. Check your VIN for open recalls.

Likely causes

1. Failed inverter coolant pump. The most common cause owners report. Bearings wear out.
2. Weak 12V battery. Can trigger hybrid warnings.
3. Low inverter coolant or air in the system. Bleed it after any repair.

What it usually costs

One owner paid $282 total for a pump replacement and said a Toyota dealer charged about $500. The pump part number owners cite is G9040-48080.

Is it safe to keep driving?

Not for long. The hybrid system may cut power to protect the inverter, which can leave you slow in traffic. Get it checked soon. Verify with a mechanic.

DIY or shop?

DIY possible for handy owners. The pump is reachable, but you must bleed the inverter cooling system afterward. Otherwise use a hybrid-savvy shop.

Recalls, bulletins and complaints in plain words

• Inverter recalls 11V342 and 13V396: These are different from a failed coolant pump. A power module inside the inverter (the IPM) could be damaged by heat on 2006–2008 RX 400h, turning on several warning lights. Dealers replace the IPM. A dealer can tell you whether yours was done. If your car is part of this recall, the dealer fixes it for free.
• NHTSA complaints: 82 keyword-matched complaints for Lexus RX 400h 2006–2008 (of 430 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-22; keywords: check hybrid, hybrid system, inverter, water pump, coolant pump, loss of power, shut down, P0A codes). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In 2006 RX400h P0A05 on ClubLexus, an owner at 230,000 miles had P0A05 with Check Hybrid and Check VSC warnings and power loss. Members said the inverter pump (G9040-48080) is a common failure, mentioned P0A93 as a related code, and said to check the 12V battery.
• In RX400h Check Hybrid System, Check VSC System warning on ClubLexus, an owner's inverter coolant pump failed at 146,000 km. The total was $282, and a Toyota dealer charged about $500. Members pointed to the bleed valve on the inverter radiator and said the pump's bearings had failed.

Quick tip

On an older Lexus or Toyota hybrid, check that the inverter coolant is moving. It's a 30-second look.

Vehicle focus: 2006–2008 Lexus RX 400h. The Toyota Highlander Hybrid of the same years has a similar setup.

Safety / mechanic note

The hybrid system can shut off power to protect itself. Verify with a mechanic.