Used 2001 Prius battery dead

Well, I just got through going through the same situation if you look back and find the threads on my 2002 Prius I bought a few weeks ago with a dead battery.

Do you have a scan-tool? Any engine codes would be helpful, even from a standard OBD-II scan-tool.

But essentially what you should see is the screen in the center-console that shows an icon of a battery with the word MAIN above it. That will be the key.

I ended up buying this one anyway since I talked the guy down to $2,800 so I figured I couldn't lose. Putting in a new battery seemed to cure everything. But I'm not done yet because there is a lot of other stuff needing replacing. I already put new tires, new spark plugs, some tail lights, and I'm about to do the coolant and transaxle fluid.

 

You might consult with:

Remanufactured Hybrid Vehicle Battery Packs

 

Instead of seeing the MAIN battery icon, you might see the icon with a car and exclamation point in the MFD. That is the hybrid system warning icon.

To be sure, you need to have the DTC read. A generic OBD-II code reader may not pick up DTC logged by the hybrid vehicle and traction battery ECUs. DTC P3000, P3006 and/or P3011-P3029 would indicate a failed traction battery.

 

True. Mine intermittently showed the car and exclamation point too, but always showed the battery.

 

By the time you tow the car to the dealer and pay them to scan it, you could have bought 4 or 5 scan-tools. I suggest you buy one. Even a $50 scan-tool will show most of the codes needed to diagnose something like that. I found that my regular OBD-II reader that I paid $100 for a few years back would actually read the codes on the Prius as long as it was a code that caused the check-engine light to come on, and something serious in the hybrid system will cause that. Of course, you'll have to look the code up on the internet to find out what it means, but you should still be able to see it.

 

A generic OBD-II reader should be able to read DTC logged by the engine ECU. However it may not read DTC logged by other ECUs, such as hybrid vehicle and traction battery.

You might be able to read one or two DTC using a generic reader - however that may not provide the complete story. Since the OP is concerned that multiple problems may exist with this car, it would be good to know all DTC that have been logged.

 

I was told the same thing by my toyota technician friend. The reason he thought that was true was because when they plug in their $10,000 toyota scanner, it shows DTCs and exactly which computer it came from. But he never sees hybrid codes coming from the engine computer. However, I found that my OBD-II scanner would pull all of the same codes through the engine computer. It appears that the vehicle's computer recognizes the fact that the scanner attached is a generic scanner, so it goes ahead and sends the codes that way.

I'm going to theorize that it has something to do with the fact that the hybrid system is part of the drivetrain and emissions system, so by law it probably requires this.

It is true that the airbag computer, ABS computer, etc, will probably not show up on a standard scan-tool, I think most anything needed to troubleshoot probably will.

 

Why, exactly do you think the transaxle would be bad? You mention a code P3009 but you also said you haven't had the codes read on the car yet, so where are you getting that? Also even if you have a P3009 that is a high voltage leak and can be caused by a bad battery too.

I haven't really heard of any significant issues with the transaxles. My toyota technician friend tells me the only transaxle in a Prius he has ever replaced at the dealership was because somebody had accidentally put the shifter into PARK while the car was driving. In this case, the transaxle still worked except that it would no longer lock the wheels in park.

The most common problem I see with Gen-1 prius with 100,000+ miles is having a dead HV battery. And that is easily fixed, although somewhat costly. Yet at the same time, if you buy the car cheap enough like I did then the cost of a replacement battery is easily offset.

 

The transaxle failures are much more rare than the battery failures. Probably more rare than lower quality cars but better documented by the enthusiasts of these cars.

I got mine cheap too with a bad transaxle and replaced it myself. That one went because the previous owner punctured the sump and it ran dry.

Do try a generic scanner. It should give you all the main codes. Then we can help you go from there.