New-used 06 Prius - P0AA6 & C1310 52 hours later =(

Hi all,


I've been scouring these threads for a few days now. Tons of useful information I'm very grateful for. I have seen the P0AA6 mentioned a lot, and a few P0AA6+C1310 threads. I've done my best to ensure this isn't a repost. If I've missed the answer somewhere, my apologies and thank you for pointing me in the correct direction.


Bought the Prius Tuesday evening, Friday morning I get the red triangle and car won't ready after parking and having been turned off. Got it towed to a shop that doesn't specialize but does work on hybrids. Really nice people, but based on everything I've read here and a bit elsewhere, I questioned much of what they had to say. They claim it's the traction battery that needs replaced and it will definitely solve the problem. Since they had previously mentioned the inverter, I asked if that was being replaced too and they said it's the same thing. I explained I thought the inverter was in the engine compartment and is a completely different piece of the puzzle, and they stumbled to restate that it would just be the battery pack but they are the same thing and listed in inventory as the same thing. His tech did a test through their MODIS/MOTIS (?), which I presume to be the OBD interface talking to the battery computer, and that 12/14 cells (I assumed he meant pairs of cells and guessed the battery computer tested them in pairs to simplify things a bit) were bad. There was much said that I won't dive into which made me question their diagnosis despite their claim to guarantee their work. I didn't want to drop $3k on the wrong part, so I decided to bring it home...


Got it home and into the traction battery pretty quickly even with being methodical and prudent. Far simpler than I would have imagined. There was a very minor amount of corrosion, nearly nothing for a 10-year old battery. Put my multimeter on each cell, consistent 8.11-8.13 volts on every single cell. I haven’t performed any cycle testing, but having that voltage seems to almost eliminate the cells as being bad. Or am I wrong on that?


The P0AA6 is supposed to mean a ground fault, no? And it is accompanied by a location sub-code, right? I’m new to the idea of a code beyond the old school obd2 diag codes, so this is new to me. But, when I asked the shop if they had the sub/info code, he said he knew of no such thing. I ordered a Mini VCI and will hopefully get to grab the codes myself at some point. I had a Bluetooth OBD but I didn’t realize it wouldn’t pull codes on a hybrid, so that was a fail when I tried to use it before it was worked on.

My wife has a 2015 Prius, we’ve had a Camry hybrid, and a Prius C (2012) before as well. I’m accustomed to the various noises made at various stages of operation from Toyota hybrids at this point. Well, this one has a particular but subtle grinding whine that seems to come from the engine compartment at the point of traction motor engaging. It sounds off, but it’s not so bad that it concerned me greatly. With all of this new information, I started looking into it. I pulled the cover panel in the engine compartment and looked at the inverter area. Nothing indicated it had ever been worked on—no sign of bolt removal, etc. But the (I assume) inverter coolant tube had been moved at some point for sure. I don’t know if it has to be in order to change the fluids, or maybe it was disconnected and moved to get to something else, but nothing else really had the appearance of ever being bothered with.


Once I get the VCI going, hopefully I’ll obtain some more isolated fault codes to work with. But, does anything I described stink of a particular problem to anyone here?


Any advice or tips on more thorough testing I could perform on the individual cells? If so, a precise technique would be appreciated as I’ve not done any kind of battery cycling/conditioning/load-testing on NiMH. I was considering purchasing an NiMH smart charger capable of cycling these cells (7.2v 6.5Ah, correct?), but I expected to find a few cells that had lower voltage. Thinking about cycling all 28 sounds tedious doing one at a time, and possibly unnecessary with the kind of voltage they appear to be holding (~8.12v). Is there a length of time I can wait (24, 48 hours, etc.) where I can test cell voltage again and have some kind of expectation as to where they should be / maximum acceptable discharge?


Are there any on-the-cheap ways to test some of the likely components, such as the traction battery ECU, transaxle, inverter, AC compressor (which I keep reading is one of the specific locations for some ground faults), or any other likely components?


All advice and comments are welcome. Thank you in advance!

 

Ah, forgot that major bit of info. Sorry! 162k miles

I took some photos earlier and just went out to take some of the underbody of the battery pack (as best I could given it's not removed, just uncovered).

I don't see any noteworthy corrosion underneath. There was some on the terminals before I unscrewed them, but it was minuscule. There is some minor corrosion and rust at points away from the cells as well, but don't appear to be related or excessive at that.

There are also a few photos of the area around the inverter where I found the moved coolant hose. Everything looked in good shape there as well, though. No sign of any surface damage to my untrained eyes.

 

Good idea, thank you! I just tested and there was no voltage between it and any of the terminals on either end of the adjacent three cells.

This did get me thinking, though, about the basics. The high voltage lines are supposed to be isolated from the rest of the car, basically, right? Hence the ground/isolation fault. So I'm wondering if there are test points and resistance criteria defined by Toyota anywhere. In other words, a mapping of places to test resistance and their corresponding tolerance thresholds.

I would think there would be something somewhere, as ultimately this is the best way to isolate any degree of shorting of the high voltage system to the rest of the vehicle. It's sort of what the ECU is doing automatically, which triggers the fault in the first place if it finds a threshold exceeded, or sign of a leak. I read somewhere on here that there is a 1kHz signal (or so) injected into the high voltage system, and that signal is being monitored at various points to detect and locate an area of degraded resistance.

Is there perhaps a troubleshooting guide available that enables techs to test these points manually with a multimeter or other equipment on a disabled vehicle?

Out of curiosity I did some random resistance tests of the high volt system against a common ground point. The two leads that go from the battery pack to the inverter and motor had some level of connectivity. The resistance was in the megaohm range on both if I recall, but that of course means nothing without knowing the threshold design thresholds and using the specific test points. Frankly I was a little surprised it didn't stay out of limits from where I was testing, ground at back of vehicle against feed cables going up to ev motor.

 

Hi Patrick,

Thank you for the info, I'll give that a try this morning.

I can't recall precisely but I vaguely recall minimum insulation resistance being 1 Ohm or 1 k Ohm per volt. Does the manual specify 10M at every test point? I don't have access to TIS, but will look for the manual elsewhere when I get back from my appt.

I have a Greenlee DM-100 which says its range is 40 M Ohm. Is there any reason this wouldn't work for the tests?

Thanks again!


Merged.

Hi edthefox5. The battery thus far doesn't appear to be bad at all. In fact, it looks to be in surprisingly good condition versus what I expected, and the voltage is excellent.

I am going to use Patricks 10M Ohm test plan and see if there is anything of note there. But, the cabling looked in good condition where it was visible.

I fear it is the transaxle, but am hoping it's the inverter or AC compressor. The transaxle seems like it will be the most difficult and probably expensive to replace. I'm not sure the grinding is from the transaxle. It's subtle, and it's not exactly a grinding sound but a grind/whine, hard to describe.

Does the trans fluid have to be drained to be examined or is there an easier way, such as the reservoir?

Thank you!

 

Wow, thank you! This was verrrry revealing. There were three visits of note:

• 2012-08-21 - New HV battery!
• 2016-01-16 - Red triangle, won't go into drive (sounds familiar!)
  • So far, this servicer has refused to provide a copy of the service record. I left a message for a manager
• 2016-01-30 - Another servicer, same problem (Guess it was a second opinion or failed repair?)
  • This is getting faxed to me now

So, the 2012 HV battery replacement along with it being in such apparent good condition with good voltage supports the idea it's not the battery at all AND that the mechanic shop I just endowed with over $400 (included a 12v battery change) diagnosed incorrectly. I have the service/tech manual now. I'm going to look through it to see if it has a battery cell test procedure.

This is all great information, some good news, and some potentially bad because it is definitely shifting focus to the front of the car--a place that seems to get more expensive. But, progress is progress and I'm very thankful for the help you've all given.

After reviewing the service manual, I called the shop that diagnosed the problem to clear up the conflict of information I'm seeing. They adamantly stood behind their diagnosis yet couldn't answer some of the basic questions I found here and in the manual. They don't know what an INF code is... They questioned whether the "ID4" was what I was asking for, but I informed them that that's the TPMS transmitter not being read. They really let me down at this point and I'm discouraged that my gut was probably way off about them being a good shop initially.

They won't accept the fact that I tested each battery cell holding 8+ volts. They don't know how many cells are in the prius battery pack. They don't know they are 7.2v NiMH cells. They refused to accept my conflicting data despite having a degree in electronic systems and having worked on F16 aircraft for years in the USAF.

So, he agreed that if I can have another master tech state that the P0AA6 and C1310 codes are not indicative of a weak battery (which I said were more in the P30** series of DTCs), that he would admit his master tech who is allegedly hybrid certified gave a wrong diagnosis and they would refund my diagnostic fee. I told him I really just wanted my car fixed. Nonetheless, if they diagnosed it wrong I would love to know and to have them know so they don't go around wasting hybrid-owners' money.

Do any of you know of a master tech who would be willing to comment on such a thing?

The facts:

1. DTCs:
   1. P0AA6 (No INF given as they don't know what that is)
   2. C1310
2. Every cell, in complete isolation, measures 8.11 to 8.13 volts, steady and consistently. I just measured five of them (this is about 24 hours later) and they're at 7.96 volts. I'm not a battery guru, but generally speaking I think for 7.2 volt 6.5 Ah cells, a bad cell isn't likely to hold this voltage for very long if at all. It's possible, but not likely.
3. The battery pack was replaced by a Toyota dealership in Aug 2012 at 125k miles (we are now at 162k miles)

 

Steve, thank you very much. I'll continue to refrain from any 100% certainty assertions as I typically do. I definitely don't eliminate the battery pack as suspect, just that the observations and information I've gathered to this point have started pointing elsewhere.

So you're saying you tested voltage between the metal framing where the liquid (possible cell leak) resided (which is common ground to the entire vehicle), to the cell terminal near the leak? I did this test on both poles to the leak area as well as to the frame itself near the leak. Did I misunderstand what you were asking me to do? After I post, I'll go volt test again from the leak area to all cell terminals, just to cover all extreme possibilities.

Are there any other tests you recommend with regard to isolating fault to or away from the battery? I believe most of the posts I have seen on this site have pinned p0aa6 to the transaxle, AC compressor, or inverter. But are you saying it's definitely not those things and definitely is a battery issue? I really wish it was a battery issue, because I feel comfortable with it as well. But, all of my troubleshooting thus far has left me with the impression that it's the wrong place.

I understand the "master tech" spiel, and I don't place any level of competency expectation on it. I hesitated to mention my own background and education because it's a common fallacy for people to fallback on that safety net. The correlation between education, certification, and even age and experience, is loose at best to competency. I haven't and refuse to take anything they say as gospel exempt from need of any validation. I know many do, including the deluded techs themselves, unfortunately, and it can be extraordinarily difficult to break through that delusion. Right now, it's a both because I've dumped money on them and wasted days I could have been just troubleshooting it myself. However, if I'm going to have any chance at compelling the dealer that sold me this car to share some of the loss, it's going to require "qualified" opinions, regardless of if there is indeed any quality to those opinions.

Thanks again for everything, I'm out to the garage to do some more testing. If I don't find anything with the pack or the resistance testing suggested by another, I'm going to button her back up, prepare a Windows XP virtual machine on my laptop, and drive around until I get the error.. because my VCI just arrived =) =)

 

Results of resistance and potential testing at various points

1. All cells still at 7.96 V (they were 8.11-8.13 V yesterday)
2. 0 Volts between ground (at the wet spot S Keith noticed) and all cell terminals
   1. Out of Limits resistance (Open Circuit) between ground and all individual cell terminals
   2. The wet spot is 0 Ohm to low-voltage ground, as are the mounting bolts at the bottom of the cells. Thus, item #2 above means none of them would have any connectivity to the terminals either

Now, a few ohm tests between various points of interest. A small few of these are completely redundant because I annotated the test points on my phone before looking closely at their interconnectedness, and so some of those weren't measured once I realized. * All ohm tests are to low-volt/common ground unless otherwise noted

1. Results for points in the image below (traction battery main terminals, ECU, and what I can only guess is the signal injector):
   1. The ECU enclosure - 0 Ohm to ground
   2. 0 Ohms (CTG/Closed to Ground)
   3. 3.2 MOhms
   4. Same point as #7
   5. O.L. (OTG/Open to Ground) - These are the supplies from the cells, but are completely disconnected from those and the safety disconnect is removed as well. So, almost pointless to mention, but it's labeled so...
   6. See #5 ^
   7. 3.3 MOhms when connected to load as pictured
      1. Terminal OTG with load wires disconnected
      2. Load wire still 3.3 MOhms after disconnect
      3. Shield is CTG as expected
   8. 3.25 MOhms
      1. Same as above with the slight ohm value difference
   9. I guess I forgot the number 9 existed while labelling =D
   10. Yellow, Black, and White leads = CTG
   11. CTG

1. Results for image below (inverter feed lines and receptacle)
   1. OTG
      1. Both shield and axial/inner conductor (power carrier) are fully open to ground -- they are completely isolated and disconnected at the source end at the time of test so this is expected
   2. Same result as #1
   3. Shield is CTG ; axial conductor 3.2 MOhms
   4. Same result as #3
   5. Surface cover is apparently nonconductive (OTG) even though it resembles a light allow metal. The mounting bolt slightly to the right is CTG, though

1. Results for image below (feed from inverter that appears to go to AC compressor, haven't confirmed yet but it heads in that direction and seems to fit the bill. Please feel free to confirm or correct.)
   1. F (on right) 4.7 MOhms ; M (on left) OTG
   2. F 4.8 MOhms ; M OTG
   3. F 4.9 MOhms ; M OTG
   4. Shields are CTG on both sides as expected

Then there's the two fat orange cables going from the inverter. You can see one in the image below, it's the orange one near the back (top of image) in corrugated tubing that has a fat, flat, black plug. I don't know where it goes but my guess is the transaxle/electric motor, or an ICE starter? Can anyone confirm this? There's one in the front that definitely connects from the power inverter to the ev motor.



My own thoughts so far:

1. The battery pack is very well isolated as are the supply lines. I believe the locations that are closed to ground are by design. No problem there with HV leakage, so probably not the source of HV leak if there is one. Since all the cells tested well and hold voltage well so far without load, and there was no continuity or voltage between the moist spot, I can't think of what could be wrong with it other than maybe faulty ECU or signal injector.
2. The AC (if I'm correct in where those lines go) could not possibly be the source of any potential leak with the all-around opens/out of limit readings (except the shield as expected).
3. The inverter and remaining connected components (no AC, no battery or supply lines) are the source of all the observed continuity, no matter how small. If this is indeed a leak issue, it's likely here.

So, my next step I think will be to drain the fluid and inspect (not sure if my eye is trained on what to look for).

I would like to get an idea of all the potential leaks from the inverter itself, ie what all it is still connected to that I couldn't identify. Are the two large cables going down to the ev motor and whatever else the only connection it should have to the rest of the world now, or does any electricity flow directly from the inverter into the motor below the inverter, via the mounted connection?

I'll be looking into the manuals a bit more for answers, but maybe someone here already knows.

Thanks again!

 

Thank you to S Keith for pointing me to the exact page number in the HV manual.

Since I received the miniVCI I decided to go that route first. I will drain the fluid eventually and perform the remaining tests. However, I'd like to know what the INF codes have been before I go in and potentially alter that. I reconnected the HV system, buttoned up the battery, and went to start the car. Now the funny part... Hmm, red triangle. Okay... hookup VCI... damn there's a new code! P0A0D? Really? I messed something else up entirely now... So I try the DTC clearing a few times and it pops immediately after clearing. Again. So I search Google and had a nice DOH moment. I look back at the DTC on techstream and wouldn't you know, the five or so words right there tell anyone with attention span greater than a goldfish what might be going on. I didn't push the interlock down to lock it. So, cleared again and car started. Drove around a bit, no luck getting the red triangle to show. But, I'll be ready when it does.

Steps 18-19 on HV-434 are where the troubleshooting should ultimately end I'm thinking. The result will definitively resolve the question of whether there is a real HV leak in the inverter or transaxle.

I'm a little perplexed by the manual, though. On pg 435, the top-left figure shows U,V,W on I14 and I15 as pointing to the terminals in the inverter. However, para (e) states "measure the insulation resistance between ... on the transaxle side .. and the body ground". Well, the cables, not the terminals pointed to in the figure, are the transaxle side. Based on the steps and actions that follow, it makes more sense that they really mean what's in the text (transaxle side) not what they're pointing to in the figure, the inverter terminals. The inverter and transaxle are disconnected at this point, and if you get OK readings you are to replace the inverter assy. If the readings are NG, you are to go on and test the frame wire (batt supply line). The arrows are wrong because you'd be testing the inverter at step 18 and if your readings are good, you would not want to replace the tested-good inverter as that makes no sense. Anyway, just wanted to put that out there in case someone can point out something I might be missing.