if you ever got code P0AA1 and your car will not start here is why .
SOne models Es hybrid , Prius , UX hybrid,etc etc will got issue with relay that got stuck.
When relay for stuck you can't start the car.

 

Relay looks like this one ,and usually got stuck due to high voltage ,leaking one of hybrid cells or very cold weather,or any moisture .

 

My code was P0AA1with subcode 233.
After so many testing and checking all fuses and fusible link and bunch of relay's we got nothing .
​​​​​​Later on one other es 300 h my friend car got P0AA6 CODE .....high voltage issue.....
we open his battery and discover one bad battery cell on the block 01.It was leaking.We have replace that cell with another used and reconditioned one and that code was gone.
in my case I didn't have any bad cell but code was there and one Prius with same code.Both cars will not start .pizitive contactor stuck closed

 

We took hybrid battery out removed all cells flipped every second one to do one side positive and other side negative only After that we used aluminum wire to connect all positive and on the other side all negative ,that was way how to BALANCE all cells.After 4-5 hours ,we oriented battery cell in serious connection and put back but still no luck

 

This method for balancing was working great on most of hybrids .Our problem was still code P0AA1-233 .and here is what we did found out.

 

During balancing we had to remove relay box assembly.After checking with instrument some resistance and voltage later on we have established that one of 3 relays not working Since dealer will not sell individually relays we had to buy all assembly

 

Es 300h relay assembly

This is Prius ,hybrid relay assembly

First we have replaced all junction box relay assembly on Prius as you can see from picture and voila car started right away .NO MORE CODE P0AA1 -233.

 

In conclusion ,hard to believe that this relay junction box has full control of the car and if any of those relays got suck you won't be able to start car at all ,but you will be able to read code . So this is how we solved problem with all hybrids with code P0AA1,P0AA6. ENJOY YOUR HYBRID ,CHEERS

 

Are the photos of your Es or a Prius?

 

photos are from ES and last 3 pictures were fro,m prius just to compare both relay junction boxes are same with difference of main plus and minus connectors .As well as mounting location ES JB is mounted on battery white holder bracket and on prius JB is outside of the hybrid battery cells.really doesent matter which hybrid you drive looks like all of them got JB relay isue related to this code P0AA1.This was working in our c=ase some other cars could have different approch...all this was just for educational purposes