P0aa6

Then again, some may not.

 

You never can tell.

 

I replied to your other thread. There is a "sticky" in the Technical section

http://priuschat.com/forums/gen-ii-prius-technical-discussion/58920-transaxle-failure.html

Hope this helps

 

P0AA6 is a 'hybrid battery voltage system isolation fault'. The car will drive normally until you turn it off, then it won't go into READY. It indicates that the car thinks that there's a possibility of shock from the HV battery, because there was an unexpected voltage drop somewhere in the system.

This code was changed between 2005 and 2006 model years, by SAE's request. 2005 and earlier cars - with tinted brake light lenses - report code P3009.

I would do a lot of testing with a megohmmeter, as described in the service manual, to ensure it was definitely the transaxle that was faulty. It's an expensive and complicated part to replace.

 

It still sounds like the cvt needs to be replaced. But I wouldn't have any faith in your dealership

 

Continuously Variable Transmission

I'm going to research the DTC and your measurements a bit more. Hold off on ordering an expensive part until you have all the facts

 

Still researching

 

According to the information I have for a 2004 Prius, the Pa006 code isn't used. The P3009 requires additional troubleshooting, depending on inf reported

Eg inf 526 requires checking insulation. For example, you're supposed to use a megger to check with the connector detached, service plug open in rear, everything off

The first check is at the connector shell, which tests the wire insulation to the back of the car. Using the megger with one end to body ground and the other end to each of the 3 pins, the insulation resistance should be 3 Mohm or higher.

With the plug still disconnected, using the megger at the cvt case, each pin to ground should be 2 Mohm or higher.

You're supposed to carefully check underneath for the condition of the hv cables. With everything still disconnected, you're also supposed to check the battery ecu and the main power relay for sticking.

Inf 526 lists the following possible problems:

Frame wire
System main relay
System main resistor
HV battery assembly
w/motor compressor assembly
Battery ecu
HV transaxle assembly
w/converter inverter assembly
Main battery cable
Main battery cable 2
Battery servicing plug
Frame wire 2
Junction block assembly

Inf 613 concerns the cvt m/g's and/or the inverter converter. However, not sure why both 526 and 613 would be set

Each step requires additional diagnostics to rule them out. I wouldn't go just replacing parts, especially expensive parts. It sounds like your dealership is incapable of performing proper diagnostics

Toyota Europe offers a subscription to very detailed diagnostic procedures. It is probably worth your while to subscribe and learn how to do these diagnostics, as a replacement cvt is +$4,000 usd

 

Unless the impedance from the HV battery to ground is low, I don't see a risk in not fixing this, if it works OK otherwise. I think that the problem can be fixed with 2 balancing resistors between the battery + and - after the relays and ground. I suspect the computer looks for an imbalance in the voltage + and -. Anyone no for sure?

 

The battery ECU is looking for a ground fault with the high voltage lines. All high voltage (the + and - sides of the traction battery as well as the 3-phase AC) is supposed to be totally isolated from ground.

The OP's vehicle has a ground fault in a component. It appears that the OP disconnected the MG1 and MG2 cables and found that some of the MG terminals have less than infinite resistance to ground. This is proof that the MG stator windings have a short somewhere. Disregarding the safety issues associated with that, the transaxle is not going to perform much longer with a bad MG winding.

 

How much lower resistance did Mahen find? If it is very low, I would agree and replace the CVT. However, if it is 100K or 10K instead of 10M, the fault may have no effect on operation, and may not fail further for years. There is probably no way of knowing without seeing what happens. If it was my car, and the impedance was high, I would try to find away to not get the DTCs without changing the CVT. There is really no danger from shock in the car, only under the hood near the invertor, if you hit a battery contact and the chassis.