Bad transaxle?

(This may not be on track at all, but I feel I have to mention it)

If the 12 volt battery was failing, the computers would not get enough power to work reliably. They would produce random codes that were not all about the same topic. How old is your 12 volt battery? When was the last time you had it tested?

Entering Maintenance Mode (aka 12V Battery Check) without Switching Headlights ON/OFF | PriusChat

 

Yes, that is a reasonable theory. To prove it, disconnect the high voltage wires at the inverter which lead to the transaxle (two sets of three wires each, because the inverter connects to both MG1 and MG2). Use a megohm meter to see whether there is any measurable resistance between each wire and body ground.

If the transaxle has a really bad problem, a regular ohmmeter might work. A megohm meter is like an ohmmeter except it uses high voltage to provoke an insulation breakdown.

 

Yes, you can clear the DTC by disconnecting the 12V battery.

It would not hurt to give the 12V battery a good overnight charge while it is disconnected to make sure that is not contributing to the problem. A new 12V AGM battery will measure ~13V after surface charge has dissipated.

The high voltage ground fault potentially could be with any component which handles high voltage. if you get the megohm meter, you can test every component exposed to high voltage except the traction battery itself.

To test the traction battery, you would measure voltage from the positive and negative terminals of that battery to ground. If you measure any voltage to ground, then the battery itself has a high voltage ground fault. This could result from electrolyte leaking from a battery module, or perhaps a problem with the traction battery ECU where the wiring harness connector has developed the ground fault.

 

Hybrid iso fault means one of the phase windings has suffered a burnout and the Inverter is sensing a ground fault ie voltage finding ground when under drive. There will be an accompanied shudder also from the front passenger side.

If you absolutely need to be convinced and this is alot easier than ohming the trans legs is dump the trans fluid and it will smell pretty burnt
and you may find pieces of the winding coating..

How many miles and have you ever replaced the trans fluid.

 

Yeah sorry to say not looking good. Trans failures are pretty rare but definitive in there failure symptoms.
In the G1 a ground fault will shut the car off. In the G2 it allows you to drive. You can reset the 12 volt battery and continue driving for a while till the gf dtc shows back up.

Go to lusciousgargae.com as there really good at this and lots of blogs to read about blown transaxles.

 

But btw, continue driving and it can eventually damage the Inverter also making recovery that much harder.

Find a used transaxle and throw it in.

 

If a battery module had failed, then DTC P0A80 would be logged. Usually another DTC, P30xy would also be logged to pin down which module pair is at fault, where x = either 1 or 2.
However if a battery module is leaking electrolyte, that would be the cause of the high voltage ground fault and P0AA6 would be logged.

I believe the transaxle is covered under the 5 year/60K mile powertrain warranty. But you can ask and see what happens.

 

Pretty sure I am going to be doing this shortly. Any idea how much replacing with a used transaxle on a 2005 should cost, ballpark? It has 350,000 miles on it.

 

prius transaxle | eBay

better set aside at least $300