What the inverter does
A hybrid or EV battery stores direct current. The electric motors run on alternating current. The inverter converts one to the other, and on many hybrids a boost converter raises the battery voltage first. A separate DC-DC converter keeps the 12-volt battery charged, doing the job an alternator does on a gas car.
Common symptoms
- "Check Hybrid System" with the car refusing to go into Ready
- Sudden loss of power or a reduced-power mode while driving
- Inverter cooling codes such as
P0A93on Toyota and Lexus hybrids - A 12-volt battery that keeps going flat, which can point to the DC-DC converter
The cooling pump comes first
The inverter has its own coolant loop and electric pump, separate from the engine's. When that pump stops, the inverter overheats and sets codes. On some Toyota and Lexus hybrids the pump is a well-known failure, and replacing it, then bleeding the system properly, fixes the problem without touching the inverter itself. We always check pump operation and coolant flow before condemning an inverter.
How we diagnose
- Full scan of the hybrid control modules, with freeze-frame data for each code
- Inverter coolant level, flow and pump operation
- High-voltage insulation resistance testing, measured in megohms, to find leaks to chassis
- Checks of the high-voltage wiring and connectors between the battery, inverter and motors
Toyota and other manufacturers have issued recalls and warranty extensions on some hybrid inverters. We check your VIN for open campaigns before we quote, so you don't pay for a repair the manufacturer covers.