Hybrid battery ground isolation question (re P0AA6 DTC)

Where are you in the usa or which metroplex is nearest, as the country if fairly large still. Maybe another member could assist or help you.

Don't believe there is an App that can read the INF(s) / subcodes / detailed codes. You can use a mini-vci cable, and techstream for such.

Sounds like greenbean has installed a failing battery, most likely knowingly. Next time test drive it twice to make sure it starts a second time.

Have you tried disconnecting the 12v battery, which may allow the vehicle to drive until you power it off again? (rinse and repeat as needed)

If the above works (resetting the 12v, then 'power cycle' twice), and the cars drives, then take it to greenbean for a warranty claim (INF 612).

FYI : your posts are being moderated until you've posted 5 times.

 

See if @PriusCamper is driving in your direction, as he can scan with techstream for a screen shot that you can use.

There are some handheld obd2 scanners that offer INFs or subcodes/detailed codes, an advanced search should find them. A standalone scanner may cost about the same as a visit to the dealership and add another tool to your arsenal. A mini-vci cable / techstream costs $20.

Which DTCs will greenbean consider a "battery failure", and if DTC P0AA6 is one of them, then which INF needs to accompany said DTC?

 

What's the impedance of your meter?

Do you still see 144 V if you load down the reading some more, say with a 220 kΩ ¼W resistor from your probe to the chassis?

 

I think, with the battery case mounted to the car chassis, a steady reading of 140+ volts is a bad thing...certainly means the 'leak' is from the HV battery, since the main relays are open....

 

Yeah, I just tried the same thing with my meter, which has an input impedance spec'd at 10 MΩ. I will see an initial voltage between the service plug terminals and the body, but the 10 MΩ load will bleed it down by around a volt per second.

 

You would need a mini-vci cable (or better) to run Techstream. You can use virtualbox.org/ to run winblows.

Do you need a preinstalled winblows image that already has techstream installed, or will you be rolling your own?

 

If your 10 MΩ meter shows you a 144 volt reading, and your (10 MΩ ∥ 330 kΩ) ≈ 320 kΩ load just pulls it down to 133 volts, it's like you're looking at a 144.4 volt source with about 27 kΩ impedance. That's a serious leak; the isolation ought to be up in the megohms at least, and if I remember right, the threshold to trip a leak code is still in the several hundred kΩ range.

If there is just one leak, it has to be pretty much right at the far end of the pack from the service plug (144 volts away) and the leakage path seems to have about 27 kΩ resistance.

Of course it's possible for there to be more than one leak, and taken together they happen to be Thévenin-equivalent to a circuit with 144.4 volts through 27 kΩ.

 

We could do a health check at my shop.

You are welcome to email me [email protected]

Deal with this all the time, you should be able to do the test Carolyn does in that video and that should be enough for green bean....

 

May have already been attempted : Error Code P0AA6 526, Mechanics code reader cannot find any detailed codes. What to do? | PriusChat

 

Well, when you have an isolation fault in the HV battery, you have voltage potential to the vehicle chassis- which is ground for the 12V system. And the battery ecu is the only other point where the HV and 12V systems come together when the car is powered down. So I am guessing that the leak is somehow allowing a current path from the HV battery to ground, back through the 12V battery and then the battery ecu (reverse flow through some diode maybe?) finally returning to the HV battery through the voltage sense wires.

You would have to use a low current amp clamp to measure where the juice is flowing when the fault is there.

Posted via the PriusChat mobile app.

 

I know this thread is old but I wanted to add to it.
My 2008 Prius shows HV voltage measuring from the cables coming off the HV battery to chassis ground after I started to have HV charging issues. If I pull the HV plug to split the battery, one cable from the battery to ground reads negative and the other reads positive,
meaning with one lead on Chassis ground, if I touch the other meter lead to one cable from the battery it reads positive and touching the other cable it reads as the negative side of the battery is grounded, the voltages only represent the section of the battery from the short to ground to each cable coming from the battery to the relays.

The voltage slowly drops as you read it so it is not a dead short, it is most likely a leak of the voltage traveling through electronic components in the Modules grounding somewhere.

So the sensor leads off the 14 pairs of cells lead to the HV battery module, my HV module was good, I had 2 back up modules and none of them changed the symptoms, I also isolated the case of the Battery HV module from ground and still had the voltage leak , so my leak was not because of a bad HV battery module.

But what did make the voltage leak drop out is when I unplugged the rear facing plug in the HV battery Module. The wires in that plug were terminal # 1 green/ground, #2 Blue ,"power on" control signal, #9 battery blower low speed, #10 Brown, blower relay, #12 ,+12v from battery, #13 Orange, ignition on, #18 BUS high, can bus signal # 19 BUS low, can bus signal, #24 battery blower motor signal.

The other slots in the plug had no wires in them and the only one the HV could have leaked through is the green wire.
I have another symptom, if I unplug the large wire that plugs into the 12v battery positive side connector block which all power to the modules are powered through and put my dc amp meter in the circuit there was a drain over an amp on the battery with everything powered off but after a while it appeared that current would become less and less.

So there is a correlation between the voltage leak to ground from the HV battery and the amp draw off the 12 battery when the car is powered down because both slowly drop off after the car is powered down. It is almost as if the leak is through a large capacitor and when it charges the current flow and voltage disappear.

For me it can come and go, I can be getting over 50mpg and then when the problem starts I get the triangle and christmas tree and the battery bars on my display start dropping and my mileage is almost is cut in half as I lose battery drive, But the battery cell readings in Techstream show the battery is fully charged while my display says it has no bars.

I know the display is wrong because I checked the battery voltage with a multi meter. but the car does not know the battery is fully charged so I get the codes as if the battery is bad and the battery power is disconnected from my drive.

The problem is intermittent making it harder to diagnose. I will be replacing the HV ECU to see if that could be the problem.
But I know there is a communication issue where the display loses the actual charge sensing of the HV battery. So I am suspecting one of the modules involved in charging the battery that is in the same CAN/BUS network as the HV battery ECU.

I ordered one and just my luck the ebay seller sent me a bad unit, so that is where I am so far. The P3000 and P0A80 codes can throw under any battery power is disconnected , but the rest of the time I am getting from 52 to 55 mpg so I know my HV battery is good.
I am going to keep stabbing at this till it is fixed, then I will come back here and post the answer to why the HV battery display does not show the actual battery charge sometimes and causes the HV drive to stop powering the car, ruining your MPG.