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

Where's the battery serial number located? Or are we talking individual cells?

 

Here's an audio clip of the sound coming from the inverter/MG1/MG2 area. I mentioned it in the first post or so. I can't pin down exactly where it's coming from, but if I had to put money on it, it seems to emit from the inverter.

0:06 - Friend shutting the car door (not an engine sound thankfully =)
0:09 - Engine started
0:15 - The Sound
0:17 - Again, but sort of a back-and-forth/on-off characteristic
0:18 - Again
0:25 - ICE starts, sound emits again repeatedly and seemingly arbitrarily
0:51 - I have my friend engage the e-brake and regular brake, then put in Drive, then let off the main brake so the ev motor engages to propel the vehicle.

From there it's mostly easy to make out our voices and what's going on.

 

Unfortunately, I already had the battery module put back together before I saw this and I don't have any photos with the number in focus. Next time I open the battery, it'll be the first thing I look at.

I changed the brakes over the weekend. There was a pulsating that was driving me nuts and I tend to replace the brakes on any car I buy used anyway. It was apparently the front disc brakes because a drives after swapping those didn't have the breaking pulsation. This was the first time I had ever encountered drum brakes, so that was a new experience. One thing that concerned me was when the piston on the drivers side was pushed far to one side, it leaked brake fluid. I'm not sure how the pistons are designed internally, but I am hoping it's just a symptom of being pushed so far that the hydro source becomes open to the inside chambers. I'll be monitoring my brake fluid levels daily for the next month or so to see if there are any overall changes.

And, still no red triangle. If it doesn't show in the next few weeks, I'm going to go ahead with the transaxle fluid change. I don't want to change it just to have the thing removed right after, so I'm hesitant to invest in it just yet.

Thanks again for all the help here and I'll follow up as soon as there's any news.

Cheers!

 

Red triangle finally came back today, 4/15. I also performed a battery test as described in these forums on 4/11. I'll cover both here.

P0AA6-526, Freeze Frame data in image below. If I'm reading it correctly, it took 98 miles since the last DTC clear (or at least clearing of this DTC) for this to reoccur. I also had the engine running a good while in park and some in drive with the brake on to do the battery test, so that would explain the 544 minutes to accomplish 98 miles of driving. It seems to add up. Nothing is sticking out at me as a red flag here.

I should also note that, along with the P0AA6 DTC, I get the following code. I presume they are just secondary to the HV failure (the first one definitely only occurs in tandem with the HV leak code) or completely unrelated and independent (the Air Conditioner codes might be occuring on their own and before the HV code, I'm not sure yet).

• C1310 - ABS/VSC/TRAC - HV System Malfunction
• B1421 - Air Cond. - Solar Sensor Circuit (Passenger Side)
• B1443 - Air Cond. - Air Outlet Damper Control Servomotor Circuit (w/ History)

And here is the live data at the time of pulling the code, roughly 15 minutes after the DTC popped.



Now, going through the troubleshooting tree starting at HV-426, INF 526 has you start at the beginning which makes sense since it is the most broad code there appears to be.

1. Step 3
   1. Inverter AC compressor plug on compressor side
   2. Already completed in previous post
   3. Tested >40 MOhms (my ohmeter limit) on the compressor side terminals (OK)
2. Step 4
   1. Same as above, inverter side
   2. Also previously completed
   3. ~5 MOhms on all three terminals (spec is >2 MOhms, OK)
3. Steps 5 thru 16
   1. HV Battery components and frame wire
   2. Previously completed most of the tests. The only one I didn't technically do is the small/third SMR (In steps 6 and 7), but I can't see how it would be causing a voltage leakage. I may get back into the battery to test this in the future, though.
   3. All results OK
4. Steps 17 thru 18
   1. Since steps 19 onward are apparently redundant to previous tests, the problem is now isolated to the inverter and transaxle assemblies again, as the previous electric troubleshooting seemed to suggest.
   2. Easiest next step is to drain inverter coolant and perform step 17
   3. If step 17 or 18 points to inverter, I'll refill the fluid and see if problem persists (a hopeful but probably futile effort)
   4. If they point to transaxle, I'll refill the coolant and transaxle fluid, and see if problem persists
   5. If problem persists, whichever component was indicated is at that point probably worth replacing.

Speaking of coolant, does anyone know if the inverter calls for 50/50 diluted, or undiluted LLC?

Any suggestions on the above findings and plan to resolve?

Anyone had a chance to listen to the audio file I posted? Does it have an odd sound, or is it just my untrained ear?


------------------------------
Battery test...

For those interested, I performed the HV battery test that I found on these forums. The test procedure is basically to put the car in reverse and cycle the battery with use of the accel pedal while monitoring the voltage differences of the battery cells. In one of the manuals, it specifies a threshold of 0.3 V or more between any adjacent cells as being a NG.

During my tests (I performed this about 3 or 4 times, once during the p0aa6 DTC was active), the min to max voltage almost never went above 0.1 V and usually around 0.05 - 0.1 V range. Since the min/max voltage metric/data is the lowest measured cell and the highest measured cell in the entire bank at any given moment, and the were never more than 0.3 V apart, you can safely conclude that no adjacent cells could have been out of spec. So, at this point I'm calling the battery pack OK in terms of its ability to supply power and manage itself. However, I won't rule it out completely as the source of the HV leak (p0aa6). Until the problem is fully resolved, no component is ruled out as far as I'm concerned.

Anyway, here are the HV battery test results from 4/11

 

Just checked, manual only mentions SLLC coolant, but does not distinguish between ICE vs Inverter coolant which could be a concern because:

• ICE coolant was orange-ish in color, so a regular coolant? Unless it was severely dirty, but the hue really looked orange. I would assume the ICE coolant could be traditional ICE coolant, but the manual doesn't seem to differentiate, which makes me question it
• Oil is getting dark, could use a change
• Inverter coolant looks to be the proper pink color and at the right level. The only thing I noticed was there was crystaline formations at the fill hole. Is that out of the ordinary?

 

Thanks Patrick.

1. Why does the manual call for a draining of the coolant?
2. Is the coolant still completely sealed off with the inverter cover off?
3. So the orange coolant for the ICE should be suspect, probably flushed and replaced, then. Agreed?

Cheers.

 

1. I have the 2006 manual,
   1. Which says, on step 17, p HV-433 (Hybrid Control System): "(b) Remove the inverter cover (see page HV-531)."
   2. Which says, on p HV-531 (Inverter with converter): "4. DRAIN HV COOLANT (See page HX-58)" (which itself gives the detailed procedure instructions)
2. Thank you! I just want to be sure, you're confirming that the inverter cover can be removed without draining the coolant? If so, I don't need to wait on the coolant to arrive and could get a little more troubleshooting done earlier, which would be nice.
3. Thank you again!

 

You were 100% correct. Thank you very much, saved me a lot of time getting to the next part...

After the last clearing, I've driving ~ 500-1,000 miles with no problem. Then, yesterday, I accelerated very rapidly and boom, red triangle within probably 30 seconds. So I finally got to pulling off the inverter cover and doing the final resistance tests. Here are the results.

• Transaxle to Ground Resistance (HV-433 step #17)
  • U, V, W (I14-1 thru -3)
    • BAD
    • All three leads had ~0.5 Ohms (that's ohms, not megaohms ). This lead appears to be the one that goes to MG2, which would be the one I'd assume gets the most wear since it drives the wheels.
  • U, V, W (I15-1 thru -3)
    • Good i.e. >10 MOhm (Out of Limits of MegaOhm measurement on meter)
• Inverter to Ground Resistance (HV-434 step #18)
  • U, V, W (I14-1 thru -3 and I15-1 thru 3)
    • At first the I14-x readings were bad, ~3.35 MOhm on all three. I had the supply and AC lines disconnected. I then disconnected what presumably are ECU comm lines that go back to the battery pack and the measurement turned good (see attached image, connectors labeled #1 and #2 specifically altered the reading). I wanted to ensure the inverter was completely isolated, but after further pondering these lines are disconnected in an earlier step from within the battery pack area before proceeding to these steps. If my assumption about the source of these lines are correct, then they should have technically been disconnected. I will have to search the manuals and see if I can find a concrete answer. For now I think the operating assumption is reasonable. And thus, the reader for the inverter is...
    • Good

So now that it appears to most likely be MG2, I am assuming the transaxle will require replacement. I have some transaxle fluid and was planning on replacing it if the reading looked borderline, but it's almost a short. I'm surprised nothing caught on fire. I really don't even see how it could be THAT low and still have driven at all. It's basically shorted to ground.

So now my primary question to the community is if anyone has advice on method for getting this fixed. I don't feel I am equipped to drop a transaxle and replace it. But, maybe I'm underestimating the requirement. I equate it to a transmission, but is it lighter and easier to get to? I definitely don't have a motor lift or anything like that. I have some jack stands and a very modest set of tools. Any thoughts/advice here?

And some out loud thinking:

If it's the shop, I won't take it to the placed that clearly misdiagnosed it as a battery issue. It's out of the question. So my choices are Toyota, find another shop that *claims* to be qualified to work on hybrids and interview them a little more before giving them the keys, or try to convince the shop that I know and trust that they should consider doing the mechanical portion of the transaxle replacement.

Another option is my neighbor. He works on hybrids at the Nissan dealership, and he has his own small garage where I see him always working on cars. I only know him in passing but I get a very good impression about his aptitude and ability. I only fear getting into business with a neighbor and having things go south.

 

Add on question: Based on the manual, HX-69, it appears the transaxle assy is to be dropped out of the bottom for removal. Is it also possible to lift it out of the top of the engine compartment?

 

Just an update. Transaxle was replaced almost two months ago and has been driven regularly ever since without any issues. It appears the transaxle was indeed the right thing to replace and I'm glad we didn't get talked into replacing the battery needlessly. I have written to the shop that claimed to be hybrid qualified that gave the incorrect diagnosis of bad battery. They promised if their diagnosis was wrong they would refund the diagnostic fee. Maybe they'll live up to their promise. It will earn them an extra star or two on the reviews they'll be receiving.

Thanks again for all the input, it's been a great experience. Cheers!