P0AA6 & more! Seemingly out of nowhere...

Hey guys, today I embark on the dreaded HV system failure troubleshooting process. I am not an expert, but I can definitely get things done. Would appreciate some support and input along the way. I have the P0AA6 with detail codes 526 and 612. A quick search later and I am planning to pull my hybrid battery for visual inspection today.

Our 2008 Prius has somewhere around 175k on it and has not had an easy life. It hails from the hot and dry California / west coast of the U.S. and now lives in the incredibly humid and wet Florida. It gets driven hard by Prius standards and was in a major accident early in it's life. We have owned it since 2013 with minimal maintenance/common minor issues and no major issues to speak of. It does burn a bit too much oil for my liking but I check it weekly and it is no longer my primary commuter car so it is living a more relaxed life with my wife these days. It has a faulty combination meter / dash board and some other minor codes I have kept an eye on but were nothing major. It has definitely lost MPGs since the day we bought it, but I just attributed it to some loss of compression/oil burning and an aging HV battery. I have serviced it well and maintain my vehicles where it matters since owning it. I also have a mini VCI and Tech Stream for diagnostics.

So yesterday I started the car as usual with the family loaded up to go-to a doctor's appointment and immediately got a warning across the MFD (touchscreen display) that just said PROBLEM with an (!) in a triangle. I shut the car off in the driveway and upon restarting it, it was immobilized. We had just driven it a day or two prior for an hour long car trip with no issues all the way home. I immediately pulled codes and got the following:



I am aware of the P1121 code and already have the part sitting on my shelf ready to swap in. I also had the inverter coolant pump fail and replaced that not too long ago as well. I don't suspect my coolant storage tank (P1151 is truly bad as this code only showed up after swapping out cooling system parts- I expect a better bleed may resolve the P1151 code. The P3193 code (out of fuel is my understanding) is likely from a month or two ago when my wife ran out of fuel on the highway and had to have our roadside assistance bring us fuel. I don't think I pulled codes after that incident until now so that makes sense to see it in the history but our Prius definitely has fuel in it currently so not sure why it is also marked as a current code. Based on this link here:

07 Prius Codes C1259 C1310 P3018 | PriusChat

codes C1259 and C1310 are byproducts of the root cause code P0AA6. According to this thread here:

Error code B1421 | PriusChat

code B1421 is a BS code with nearly no meaning as I have had that code hanging around since buying the car and our AC has been working normally the entire time we've owned the Prius. Additionally, the B1442 AC damper control code has been intermittent for some years now and just hasn't been a priority to fix with how busy I am all the time. I will likely do that repair when I replace the AC blower motor as it's bearings are getting squeaky and annoying now. And finally, code B1271 correlates directly to the faulty dashboard combination meter I referenced and has been a known issue to us for several years now.

 

So this morning I disconnected the 12V battery for 10 minutes or so and allowed everything to reset/clear, then fired the Prius up to still receive the yellow triangle with (!) and "PROBLEM" across the touch screen display. However, after a minute or two, I went to cycle the car off by pressing the power button with my foot still on the brake and it then fully powered up normally. Everything was working and no indicator or warning lights of any kind were active (the dash happened to be working this morning). For some reason my gas gauge was blinking on 1 pip as if it were on E. After letting it idle and charge for a few minutes, I power cycled it off and back on a few times with no new surprises. After I felt I could trust it enough for a quick 5 minute run to the gas station less than 2 miles from our house I headed for gas. Within that 2 mile trip my gas gauge instantly flipped from E to full 10 pips. I topped off the tank to be sure and it only took 1.75 gallons so my estimate of fuel level was indeed adequate. Got it back home, still no indications of any trouble. Debating whether or not it is worth tearing out the HV battery for visual inspection or if I should just continue to run it until I get the same code again. I really don't want my wife to get stranded, but she doesn't go far and we do have roadside assistance and family/friends in the area who can help out if it ever came to it.

Is there any chance water getting in the front end from driving through puddles and/or soaked roads could have caused a misleading trouble code (ie water in the air compressor plug)?

I don't have my splash shields on the underside of the engine bay (haven't for years) and never had issues driving in wet conditions before, but as I said, now we are in Florida where it rains daily, our street is pure potholes, and we have to drive through multiple large puddles to get in and out of our house/street daily.

 

I did not see any obvious water intrusion in the rear hatch area today but I have in the past. In fact I'm pretty sure it does get wet sometimes due to the subfloor "carpeting" getting wet near the two corners by the taillights during wet periods. Never caused any issues previously however and I have not managed to pinpoint the exact point of ingress.

 

I think it may all make sense now. Our Prius used to always be parked on flat ground but now gets backed in up a decently steep driveway. Previously the water stayed in the rear and exited but now it seeps forward into the battery zone. @davecook89t may have hit the nail on the head. Check out these pics here:

 

(Also forgot to mention that in Cali it stayed parked under a covered parking area, so 80% of the rain we got stayed off most of the car. The only time the water intrusions were really noticed were after running errands around the city all day on rainy days or on our cross country road trip or other long excursions, etc. Here in Florida it is exposed completely and not under any kind of cover. We have been living here in FL for about 1 year exactly. This summer has been especially rainy compared to last summer when we first arrived.)

I found the source. Don't mind the atrocious state of the seat where our daughter has spilled milk and juice over the years... I've been meaning to clean it. See here:

 

Well in our car's case, it had the entire rear driver's side quarter replaced and grafted on from another donor vehicle. We bought the car like this with the rear quarter wheel well dent but didn't realize the extent of the reconstruction and repair until after it was too late. All in all though it's been a pretty damn reliable car that we have already put about 100k miles on in about 6 years now.

Check out the cracks where the graft was done:

 

Almost done prepping this Frankenstein nightmare of a Prius I own. Been digging out Bondo and identifying all points of ingress in preparation for sealing them all up. It's not going to be pretty...

 

My headliner, rear quarter pillar, driver's side rear seat back and bottom were all wet today from sitting in the rain for several days in a row now. The seat back/bottom sit right up against the casement for the HV battery and the path of ingress had all the sound deadening insulation that backs the interior plastics wet too along with mild puddles forming under the HV battery itself. Additionally that side and path the water was entering through and settling into the valleys of is also the same path a main umbilical from the HV is routed as well as the primary HV cable exit from the HV battery pack. All things considered and based on my specific circumstances, I believe the water intrusion was likely my cause of ground fault. Once I eliminate that issue, if the same problem comes back I will surely be examining my battery much closer but for now, all signs point to water getting in where it shouldn't.

 

Like I said, it's not pretty, but it's got a rubberized, 15 year type roof sealant (I happened to already have some on hand from recent roof repairs to the house.) Lol.

 

And since I've got it in the garage for work, I just couldn't resist checking out the HV pack:

 

2 questions:

1.) Can you recommend a *new* and *quality* pack I can purchase and install that will retain some amount of warranty?

2.) Can you direct me to a pack teardown video or "how-to"? This is my first time and I'm just looking to clean up while exploring so I have some practice when it really comes time and so I don't light myself up with 130VDC lol.

 

With my negative probe on the bottom of the battery case going down the line with my positive probe touching each modules terminal I get anywhere from 2 to 9 volts DC on my multimeter.

EDIT:

After removing all of the nuts and disconnecting the modules from each other so that each one is individual I was able to isolate the end most model opposite of the battery control unit computer. It appears to be leaking 3 to 4 volts to ground. That also seems to coincide with the leak that appears visible at the bottom on that end.