The weather is very humid and that brings some of the older Toyota RAV4 EVs to a halt due to the ground fault.... I usually clean the battery pack and the ground fault disappears.
But if I was unable to clean the pack and I was sure that the fault was not serious I would probably go for making a ground fault fake box. Let's call it FAKEGF.
Such box would consist of frequency generator, power supply, output drive.
The Ground fault and HWS Controller in the RAV4 EV generates a square wave pulse to the rest of the ECU in the car to signal that everything is OK. So if we disconnect that wire and generate the pulse with our own box the rest of the ECU SHOULD be tricked in thinking that all is ok.
Looking at the manuals it is obvious that the generated wave need to have frequency of 0.18Hz and an amplitude of 5V.
Also looking at the manuals:
Here we can see that the output drive of our FAKEGF can possibly be performed by ULN2003A chip - https://en.wikipedia.org/wiki/ULN2003A
According to the manual this is the form of the generated wave. I remember that I looked at the wave with oscilloscope and don't remember such duty cycle, so it needs to be confirmed.
And here is a possible place to connect the FAKEGF box output to. The G1 pin 6 connector of the HWS Controller. Is pin 2 a supply voltage?
I would be tempted to use a 555 chip for the frequency generation and depending on consumption feed it with the some kind of regulator to make sure the supply voltage to it is as clean as it needs to be.
I would also consider making it so that there is a switch with 2 positions - position 1 is standard behavior - the LEAKV from the HWS controller is connected as normal, position 2 disconnects the LEAKV from the HWS Controller and generates the fake signal. This would be useful for still having some kind of security during dry weather and while driving... or maybe when you do not want to burn down your house.