I've replaced the battery after eleven months in my 400h. I took the car to a local service shop (Goodyear) because I live a couple of hours from the Lexus dealer. They ran a scan and said I need a new generator (cost to replace $2,100).

The best I can tell about the 400h is that is does not have an alternator, but uses a generator. The generator is one of several engine motors in the car, and the motor that oversees the starting function is called the MG1.

I went online to see how much the MG1 lists for, or whether any used auto parts locators have any for sale. I can't find any information on replacing the MG1, either new or used.

Am I looking in the right place?

Thanks for your assistance!!!

Alan

 

I'm not buying it. No way a Goodyear shop would be able to tell you one of your major hybrid components is bad. Plus, your dash would be lighting up with warnings and the hybrid system would probably not work at all if one of the motor-generators was bad.

I have read that the 12V battery gets charged from the hybrid battery pack instead of an alternator. The motor-generators are used for powering the wheels, starting the engine, and regenerating power, and aren't directly connected to the 12V battery. The 12V battery just powers the various ECUs, electronics, and lights and does not start the engine.

I don't think any traditional battery charging test (for non-hybrids) is going to be accurate for an RX400h. You would need to see a Lexus/Toyota hybrid tech at the dealer.

Maybe you have a loose connection between the 12V battery and the hybrid battery pack (or whichever cable it uses to recharge), or it is simply due to the colder weather, or it sat for too long between starts and the battery drained.

 

From the repair manual, it looks like the DC-DC converter charges the auxiliary (12V) battery. I attached a diagnostic from the repair manual. There isn't much info on it. The DC-DC converter is in the rear deck area under the floor.

 

If it were mine I would monitor voltage with a volt meter and see the 12v battery was going down over time/driving. I would also check for load while off to make sure nothing was draining it when not running. The drive to Lexus dealer may be worth the effort. They are liberal on replacing hybrid parts out of warranty. Many times people get half off. Half off new part is usually better than full price on used part.

 

I would check these fuses first to make sure the DC/DC converter is still able to recharge the 12V battery. The upper one in the diagram is a large yellow 120A fuse, and the lower one is a small 10A.