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.

 

I read six paragraphs still wondering why you were looking at all this, and in your seventh paragraph you mention getting the triangle light and in your ninth and last paragraph you mention P3000 and P0A80 codes. Are those the only codes you're seeing?

The HV system is normally floating with respect to the 12V system. The car routinely checks for any isolation fault, by superimposing a special AC signal onto the HV DC bus and trying to detect that signal on the 12V side. If it detects the signal, it gives a P0AA6 code.

If there is no P0AA6 code, the car has not detected any isolation fault. That the HV system is 'floating' relative to the 12V system doesn't mean that a meter won't ever show a voltage between them. The meter may show some voltage that slowly bleeds away through the meter's impedance. I would reserve most of my thinking about isolation faults for cars that have given a P0AA6 code.

The display is showing a computed state of charge of the battery, and the Techstream per-block PIDs are showing you per-block voltages. You can't equate the two. There is also a battery current sensor, and the state of charge is computed internally by the ECU by watching the combined behavior of block voltages with changing current, in real time. You simply don't get enough information over a scan tool to second-guess that computation in your head.

When the car gives the P0A80 code, it is telling you that the observed real-time charge/discharge behavior shows that the battery is worn out and needs to be replaced. Once the code is set, the car protectively reduces the demands placed on the battery, trying to help stretch out the time you have to find a replacement battery before you get the bang and bad smells from the back of the car and can't drive anymore.

When you clear the code, the car is no longer protecting the battery that way, so you can be temporarily back to the MPGs you enjoy when full demands are placed on the battery. The only trouble is, the more you do that, the more you bring the day of final reckoning closer.

 

I said in my posts I would figure this out.
Yes for a while I was grasping anything that looked suspicious like my SOC not reading in sync in relation to my actual HV battery charge,
And the voltage leak from the HV battery to ground which I never had before this intermittent HV battery monitoring problem started . I could tell it was not a dead short because the voltage would bleed down when I connected my meter and would slowly drop over time to zero volts. I did realize the HV leak to chassis ground was going through electronics, that is why I ordered the next most likely module, the HV module.

After watching the HV battery sensor voltages charge equally and normally while my display had no bars, I realized an intermittent problem was causing a misread in the CAN BUS system, when the codes would throw and the triangle would show up.
.
Some other codes I probably did not mention that were thrown were related to modules that were effected by what was causing my HV battery to be disengaged. Power to other systems would be cut or lowered and they would throw a code. For instance I got a air conditioning code once because when my inverter pump stopped working, the inverter cut power to the compressor to protect the inverter from overheating. After replacing the pump I never got the AC code again.

I would have had this issue fixed sooner , because after first suspecting my HV Battery ecu , replacing it , and that not being the problem, I was focused on the HV ECU, so I order one off Ebay and get sent a bad one.

The defective module did give me a hopeful clue because it caused the Christmas tree of lights to come on immediately after I installed it and I could not clear them so it appears the HV Module controls most of the yellow dash lights and communicates the battery voltage charge in bars to the center display. These symptoms were the same conditions I was getting with my original HV module, except with my module it was intermittent.

So if anyone has issues where your HV battery is not charging properly or bars are sticking on your display and you get the triangle and yellow lights, after you have eliminated it being the Traction battery, think about changing the HV module as it seems to be the main component in managing the HV battery charing and communicating battery voltage to the display.

If your battery seems to be okay

 

Next day
Okay after another stab at this problem I found I had a bad HV ECU, the voltage leak to ground was traveling from my HV battery sensor wires, through my HV battery Module and through the CAN BUS communication lines going to my HV ECU which had an internal issue allowing the leak to ground. The problem with my HV ECU was also causing my HV battery signal no be lost sometimes which made the bars on my display to drop or freeze not reading the actual voltage of the battery. This misread of the HV battery was causing the triangle and Christmas tree of lights as well as many other generic codes in different systems of the car, some associated with the P codes and others with the C codes and even a U code to my ABS/VSC/TRAC Module, because of a loss of communication from the HV module.

Just my luck I had 5 problems show up at once, a bad battery cell in my # 1 bank, my inverter pump went out, I had corroded wires in a plug associated to my battery cooling blower, my battery plates were getting corroded and hot, and my HV ECU started going bad..

I replaced the bad battery cell, found and fixed the corroded wire connections thanks to people posting the issue online who had the problem causing a P3000 code, found my inverter pump motor was open circuit, replaced it, nickle plated all my battery plates and the terminals on the sensing wiring harness to try and prevent electrolysis and lastly found my HV battery charging issue and HV battery leak to chassis ground was fixed by replacing the HV ECU.

It was frustrating still having a problem after every fix, but persistence finally worked to fix it.