Red Triangle, Code p0AA6

You probably need to find a new mechanic, one who actually knows what he is talking about.

P0AA6 is indeed an HV system ground fault, and I have not known it not to set sub-codes. There should be at least a 526 plus one other. Sometimes it needs a longer drive cycle to set the second sub-code.

The P0AA6 can involve (usually one of) either the hybrid vehicle (HV) battery, transaxle, inverter or A/C'. You need the second sub-code to know which area is involved. Statistically, the HV battery is more common, but I still wouldn't just assume that without some supporting evidence.

So before authorizing an inverter replacement, find someone who can do a proper diagnosis.

 

Everything in the OP leads to the AC compressor circuit, where it apparently has a grounding fault. Every time defrost is used, the AC system runs to dehumidify the air that's being sent to the defrost vents.

I would probably disconnect the AC compressor HV power line at the inverter and see if the triangle issue goes away. Do some electrical checks on the compressor while it's disconnected. It may pop a DTC/CEL, but if the RTOD doesn't come on then I would think the problem is in the compressor motor/circuit.

But, if you really need/want an inverter, I have three spares in the garage. I'd be happy to put one in your car for 1/6th the price that the dealer wants.

 

I'm pretty sure @TMR-JWAP is correct. The big red flashing arrow is that you first were getting the triangle when you used defrost. That turns on the air conditioner. I like his troubleshooting ideas. Disconnect the suspect to see what happens.

 

I got a lightly used compressor for $100 and it cost $200 to have it put in by an AC shop that works on hybrids all the time.

 

The high voltage system of the car is totally isolated/insulated from the 12v system (and the car body). The P0AA6 code of which you speak is letting you know there is a significant reduction in quality of that insulation. The AC compressor is an electric motor that is powered from the HV system. If the cable going to the motor is damaged or the motor itself is failing, it could easily be the source of the P0AA6 code.

 

Good point!, @TMR-JWAP. My previous answer assumes that it's found be be a HV leak in the compressor. It could also be in the wires to the compressor as noted above.

 

Have you checked your inverter coolant level? Try topping it off. My 2009 Prius started popping P0AA6 with info codes 526 and 613 this past week. If the inverter isn't getting enough coolant, the extra heat reduces some components electrical insulation characteristics just enough to cause the P0AA6 issue. My coolant reservoir had a lot of coolant in it but it was close to the minimum marking. I topped it off because I was going on a trip even with the P0AA6 and the constant disconnect/reconnect the battery to keep driving. Today I drove the car expecting to disconnect and reconnect the battery every time i turned the engine off but was pleasantly surprised that the problem disappeared as quickly as it had appeared.

 

I'd say it was just coincidence. The inverter coolant/inverter overheating cannot influence a high voltage isolation fault.

You need to come up with an alternate theory.

In most cases, the only way to clear a P0AA6 is to remove the path to ground.

In your specific case, the codes indicate that the HV ground isolation fault is in the transaxle area.