problem with my 2004 prius

Ig-On does not enable the traction battery normally. Without traction battery, you don't have high voltage (except if you were coasting, then you COULD get it from MG2), thus nothing to start the engine, nothing to run the AC compressor. The fans will run, as they are 12V but not the compressor. Heat might work too, since there is an electric heater powered by 12V, though that will probably drain the 12V battery quick.
Only READY mode turns on the traction battery. You can hear them relays click on. I don't recall hearing them click on except in READY mode, did you?

I would agree with the dealer that the traction battery was not drained, but that some of the electronics was not getting the proper 12V at times, thus misreading or simply misreporting the traction battery SOC. In Ig-On, the SOC shows blank (which supports my statement that the HV battery is not connected here) This was proven by the fact that the engine started. You need MG1 and inverter and hybrid ECU for the engine to start, and both the inverter and MG1 need power from the traction battery, or at least generated power from MG2, and you would have to be rolling for that to happen.

Reminds me of a time in digital class lab. We were building a counter. My counter was acting real weird. Tried to trace out the logic, but it wouldn't make sense. Turns out I left out VCC on one or more ICs, thus it would sometimes get its VCC from a logic 1 input, but sometimes not.

 

I wanted to double check myself about the Huybrid battery being isolated in Ig-On mode (not Ready mode).

I put a voltmeter on the jump terminal under the hood to register the voltage on the 12V system. Off I got about 12.8V. Ig-On about 12.5V, and Ready got 14V. In Ready I could hear the inverter sing. I had the radio and AC off by the way, though the blower was on low.

Interesting thing though, was SOC was showing actual state in Ig-On, though it is blank in ACC.

I think I'll sit and read the repair manual....

 

OK, I think I have it right now. I seem to be correct about the hybrid battery being disconnected by the relays. The relays are controlled by the HV ECU, and turns them on in READY mode.

The HV Battery ECU does turn on in Ig-On mode, and can read the battery voltage independent to the system relay state. It then can relay it back to the HV ECU which then relays it to the MFD. It could also read the battery current, but since the battery is disconnected from the inverter, no current is flowing.

So, you really can't kill the HV battery in IG-On, unless you consider reading the battery segment voltages could drain the battery. That would probably take a REAL long time, like days at least, with IG-On. But even that, I doubt.

 

Something just isn't right. Why live with it? I'd take it to another dealer, 60 miles if necessary, and complain to directly Toyota about the near dealer's inability to diagnose and fix it.

 

Nor does it sound like anything I've ever read about the Prius. My advice is to take Richard's advice. Have someone else look at it.

 

No, the battery indicator in my Prius is always showing values I expect it to show based on where I have been driving.

 

What you are describing seems normal.
The battery can get as low as 2 bars on idle (not moving) before the ICE kicks in to charge it. Depending on the accessories running (such as A/C), it can get low rather quickly.

 

the snow tires will take a few miles, winter formula gas can take 4-7 mpg. so i guess we need to know how much you were getting this summer to gauge raeally.

you are in a very cold area and the colder it is, the harder the Prius will have to work. heating the occupant and the engine is a pretty big load to handle.

you dont say what you got in the summer, but if you were getting about 40 mpg then your current figures will be in the ballpark. realize that 35 mpg doesnt sound like much, but it will still be 50% better than any normal car on the road. (regular ICE autos are just as affected by cold weather if not more so)

currently i am testing this theory with my sisters car. (its a Ford midi station wagon thing) it doesnt get good gas mileage at any time. but should have winter results in a few more weeks. will post results in new thread.

 

<div class='quotetop'>QUOTE(bc\";p=\"51686)</div>

bc, this might be TOTALLY unrelated to your problem, but I'll toss it out anyway.

Friends who bought one last November (2003) drove it for quite some time without problems. Then it started having ICE problems. I don't know if it was rough idle or misfiring, or something else. Turns out one of the spark plugs was cross threaded. I don't know why it wasn't a problem from the beginning but the dealer fixed it (don't know if it was just re-inserted or replaced) and the car is fine.