2009 Prius - Warnings and will not engage.

Wouldn't surprise me if the code turns out to be P0AA6, but if your time is scarce, it's better spent finding the actual code than pursuing my guess.

 

The isolation fault could be anywhere in the car's high-voltage system: air conditioner, transaxle, inverter, cabling under the car, or battery.

Still assuming this is even the code you have, with Techstream you can also retrieve a three-digit INF code that would at least help you focus on one region of the car:



Without that information, you'd just be stuck getting access to a megger and poking around the whole high voltage system with it, nose to tail.

So as you can see, there's really no better way to spend your time at the moment than retrieving the codes with Techstream. They might even be completely different from my guess.

If you can't get to the car with Techstream until morning, just don't stress about the car between now and then. There must be other stuff on your to-do list, or or something fun to do in the meantime.

 

Funny how that diagram is drawn so not-to-scale. It makes the ECU look huge. That little column of small long-line/short-line pairs to the left of it? That's the whole stack of battery modules (accounting for much more of the real size and weight of the battery than the ECU does!). The 612 area includes everything from the orange service plug and its socket, the battery modules and ECU and their wiring, up to the supply-side terminals of the SMRs. (The load-side SMR terminals are where the 614 area starts.)

You still have the job of finding out where within that whole 612 area you have a current path between something and body ground (or something and the 12 volt wiring). But at least that's an easier job than if you didn't have the INF code, and had to look for the problem somewhere in the whole car.

The C1259 and C1310 codes that are also showing are just codes the brake system will post when it knows there's a hybrid-system issue, so those are just there because of the P0AA6. No need to be concerned with those.

The U codes I don't have a ready story for, but anyway, after the P0AA6-612 is fixed, there'll be time to look into those, if they're still present.

No, there are about a dozen ECUs in a gen 2. The one inside the battery is just responsible for monitoring its current, voltages, and temperatures.

 

Typically, a 612 sub code results from a minor electrolyte leak from one of the battery modules.

It's possible to have corrosion damage at the orange voltage sense connector on the battery ecu (and on the ecu circuit board), but that causes other problems (usually not P0AA6).

Are you planning to try to repair this yourself?

Posted via the PriusChat mobile app.

 

Yes, disassemble the outer case and inspect the base where the modules bolt down. If there's a leak, you'll often see some corrosion or discoloration on the sheetmetal.

Posted via the PriusChat mobile app.

 

Just a bit of clarification- the hybrid ECU is somewhere in the front half of the car. It communicates with another ECU, often but not always referred to as the battery ECU.

During a hybrid battery swap, it is normal to keep your old battery ECU and move it to the new battery. It won't make any difference to the keys & security system.

 

Toyota has changed the name and location and division of "labor" of the battery ECU over the years, and it doesn't surprise me to learn that a swap wasn't needed with a 1st generation car- I know very little about the oldest ones.

Either way I'm confident it won't mess with your keys & security.

 

There are roughly a dozen ECUs in a gen 2 Prius, and the ones that keep track of key registration are nowhere near the battery.

The one in the battery is responsible only for watching the battery current, voltages, and temperatures.

In gen 3 they stopped calling it the "battery ECU" (it got bucked to "battery smart unit" or "battery voltage sensor") but it still has pretty much the same responsibilities.

 

Certainly suspicious.

Set your digital multimeter to DC volts (if yours has manual range setting, go with 2.0V).

Put one lead on one of the battery module studs, and the other on the sheet metal base. Ideally you should read 0.0V.

If there is any voltage, even 0.01V, then that module either leaking or is connected to one that is.

Carefully remove the nuts and bus bars and recheck. (this isolates blocks from each other, eventually you will have the individual module(s) that are leaking).

If-once you find the problem, then you get to do research on how to fix it. "Just" replacing failed modules is cheap but is only occasionally successful.

Charge - discharge cycling modules takes more equipment, time, and knowledge. There's grid chargers that cycle the entire pack vs RC hobby chargers that do individual modules. Do it right and you can get a few years out of it. Do it wrong and it won't work at all.

Then there's "refurbished" packs (either of the above processes done by someone else, with the same possible outcomes).

Or getting a new pack - such as from Toyota. Should last 10 + years.

There's many days of threads to read about all of this.

Posted via the PriusChat mobile app.

 

What I see is the battery at the end of its life.
If you replace the leaking module, the next leaking one will appear again.
I was able to find which one was leaking only when the battery was warm, having just been removed from the car.
Unscrew all 56 nuts and remove the bus bars off the modules. Then set your multimeter to the continuity mode and hook one lead to the battery case and with the second lead touch the module terminals one by one on the left and on the right side.
The leak in the photo is visible in blocks 8 and 9.

 

Toyota OEM are available for $2250 installed around here and you get 10 years out of them. Even if you sell the car in a few years, the genuine modules will be a big selling point. Reliability of the battery won’t be a concern.

The cylindrical NiMH modules are new but many only get two years out of them. Even if the guarantee of four years is honored, repeated downtime and poor reliability is a concern.



However they are better than reconditioned which may fail multiple times in two years.