P0aa6 with no subcode after head gasket replacement

How long has the car been off the road not running while you did the head gasket job another week so how long really 9 10 12 days etc? Right after I change the engine in my car instead of doing the head gasket and all that or after I attempted to head gasket and found the skirt broke and the piston rolled over and ruined the motor. I had a bunch of these problems and turned out to be corrosion on all of my bus bars and the original 2013 battery

 

It might be worthwhile to consider getting a scan tool of your own that is able to read all of your car's codes and subcodes. It is a huge hassle to have to rely on other shops or dealers even just to find out what your car is telling you is wrong.

A lot of people find a way to run Techstream. There seem to be a bunch of other good options, too, these days. I don't know of a thread comparing them that is specific to Gen 3, but there is this thread for Gen 2 that might be a decent place to start:

Gen2 OBD2 app review | PriusChat

 

Did you remove the ac compressor cable? It is high voltage.

 

If you haven't found already, here's a second gen thread on that code:

Help with dreaded p0aa6 code | PriusChat

 

During my mess with replacing the engine in the 13 when I initially put the engine back in and hung the compressor back on the new engine which was still plugged up I kept getting an AC error code something to do with the power the orange cable part of it but there was nothing wrong with the cable it was all plugged up I unplugged the air conditioner for about a month got the car running everything like it's supposed to and then one day while I was out driving I just randomly in a parking lot at Sheetz I think plugged back up the air conditioning made the old lady turn the car back on immediately put on the air and it all started to work mind you this system was not discharged to replace the engine The compressor was removed and hung in the engine bay and then when I reconnected everything I had all kinds of power errors high voltage power errors and the main one I eliminated by unplugging the compressor that thing was drain in the battery down as fast as it was plugged up if I turned it on it went from a full battery to zero and 40 seconds minute 90 maybe I don't know but I didn't fix anything I just left it unplugged for a couple weeks and then when it got hot enough and I just didn't want to fool with it anymore I plugged it up and it started working the orange power cable to the compressor.

 

We have a bunch of threads on P0AA6 around; the weird thing about that one is how little useful information about P0AA6 is in it. There's some, but it got all sidetracked about lug torque and high connection resistance, which isn't what P0AA6 is about, and then a later poster tagged on with the same sidetrack. Most of the other P0AA6 threads are more helpful than that.

So, most of our threads about P0AA6 are in the Gen 2 forum, and they show this handy diagram for where the isolation fault is in the high-voltage system, according to which P0AA6 INF code you have (611, 612, 613, or 614).



You can use pretty much the same picture for Gen 3, but you have to remember one thing that changed between Gen 2 and Gen 3. The A/C Inverter is part of the inverter assembly in Gen 2, but it's part of the A/C compressor itself in Gen 3. That means in Gen 3, the orange cable from inverter assembly to compressor is part of the 614 area (in Gen 2, it falls under 611). In Gen 3, the only parts that can give code 611 are inside the compressor itself.

 

Poster likely meant vertical. I concur; it’s like a rain gauge, if you do something like pressure wash.

 

2010 Prius P0AA6 code and has yellow triangle with "Check Hybrid Ststem"

I get a P0AA6 code but the subcode (details) code is not known. A megohmmeter, a VC60B Vici, came today. The batteries test O K.-no leakage. I removed the A C compressor cable from the inverter. The A C compressor (on fused side) reads low at first and after a minute, goes up to 20 megohms as if charging a capacitor. On the A C compressor cable (unfused side), it is 0 ohms. The inverter reads 1.9 megohms at the battery input terminals. These might vary with humidity. I will check again tomorrow.
It seems that maybe both my AC compressor and my inverter are faulty. The A C fuse was found to be blown so I already think that the A C compressor is bad. Is my assumption correct?

 

It may very well be usually when a motor or something starts to go bad it starts to draw a lot more current than it should blows the fuse burns the wire something you blew a fuse so there's always that and then so if you fix the fuse you might want to put another known good compressor in place of the one that the fuse blew in the circuit just recently and see if that works I don't know if you can test the windings of the inverter or the motor might just testing the orange leads I imagine possibly you'd have to consult the service manual or chap might know.

 

I think that the zero ohms on one line of the compressor cable tells me that the compressor is faulty. Is that a bad assumprion? I think that all traction battery circuits (+ and -) must be isolated from the chassis. (A low voltage multimeter shows 3 or 4 Mohms.) Replacing the compressor "just to see" is an expensive and miserable job. I want to be sure that I must do it.

 

It only takes about 45 minutes to whip the compressor off unplug it and have it sitting on the ground in front of you and returning a used one from another car that you know was working well that's what I do here I don't go out and buy these things usually I have two or three from cars that I know were working capped off and closed up and in the shop in my world the compressor rarely goes bad it's usually a big leak like the one inside the car that pretty much here that makes the car relegated to win or use or something or out of here either way not too bad of a job changing the compressor if you're talking about vacuuming it down and adding gas I guess you know could be a problem for some. I'm not sure about your compressor question but I can walk outside and measure whatever you want on the known good compressor that's sitting right here almost in front of me.

 

Update: I measured the low side (unfused) again this morning. It still reads 0 ohms using the Vici tester on 500 volts. And, 1.9 Mohms on either lead coming in from the battery into the inverter. I pulled the A C plug away from the inverter and taped up the hole in the inverter (to keep inverter electronics clean). After clearing all codes, I went for a test drive. No triangle. No "Check Hybrid System". So, the 1.9 Mohm resistance must be normal. So that leaves the A C compressor.
I am puzzled why one lead of the compressor reads zero ohms and the other lead measures like a capacitor. I would think that the only thing between the 2 leads should be a <1.0 ohm copper winding and no connections to the case. I assume that the start/stop relay is in the inverter electronics.
I would appreciate it if you would measure between the 2 leads and measure to the case with an ohmmeter if it would be handy for you. Do you find that A C compressors go bad often?

 

Tom,
I was interested in how you test a compressor. When I buy one from ebay, I would want to test it right away. I understand that you can just plug in the cable to the inverter and turn it on. If it runs, is it probably good? And, the compressor should come with plastic plugs on the freon fittings to keep out moist air.
I read somewhere that I should replace the condenser along with the compressor for some reason. Is that true?

 

If you glance up to post #8 in this thread, you see a diagram of the high voltage system for a gen 2 Prius (which you do not have). That post also explains the key change between gen 2 and gen 3. To reiterate:

In gen 2, as the diagram shows, the "A/C inverter" was located inside the inverter assembly, and the compressor contained nothing but a three-phase motor. (Hence, in gen 2, there are three orange wires from the inverter assembly to the compressor.)

In gen 3, the "A/C inverter" is now located inside the compressor itself (and so there are only two orange wires, supplying HV DC power to it) that connect it to the inverter assembly.

That's why, in a gen 2, the wires between inverter and compressor fall in the "INF 611" area, whereas in a gen 3 they fall in the "INF 614" area.

That means when you try to make measurements of the HV leads entering the compressor, you are not measuring motor windings, you are measuring the input side of a whole electronic inverter circuit. There is little wonder the measurements should seem weird.

It still seems wrong to have continuity from either HV lead to the case. If I were the car, I would give a P0AA6 code if I saw that.

 

Thank you. Now a lot makes sense.
We are getting way off topic. I will go to the A C section to try to learn more.

 

I guess it depends on whether the topic is more "P0AA6" or more "after head gasket replacement".

Most of what I see in this thread seems pretty tightly on topic for P0AA6.