Check Hybrid System (P0AA6-613) Diagnosis

did you find out where the problem was? I have exactly the same problem. Driving with it for over a year now. I noticed when i disconnected mg1 and mg2 cables from inverter and checked their resistance, problem went away for about 3weeks, i tried this 2 times.

 

The slow climb of the reading to its final value shows the time needed to charge the motor to a voltage matching the tester's.

The motor takes a charge during megger testing because of two effects: its capacitance, and dielectric absorption. A motor isn't built to be a capacitor, but it does have a bit of capacitance (because its windings and its winding core are conductors separated by a dielectric, and that's how capacitors are made; can't be helped). Building it up to match the 500 or 1000 V from the tester requires storing a charge in it, 500 or 1000 V times the capacitance.

Past that point, at those kinds of voltages, more energy is still going in, more slowly twisting around the molecules of the dielectric to align with the electric field; that's the dielectric absorption effect.

MG2 is a bigger motor than MG1, more windings, more capacitance, more dielectric, so what happens quickly and less noticeably in MG1 happens slowly and more noticeably in MG2.

These things are explained in Megger's booklet A Stitch In Time..., which would be recommended reading for anybody getting a megohm tester or thinking of getting one.

If you buy a tester from one of the more expensive traditional suppliers, it probably comes with a manual that goes into those topics. If you pick up a cheaper offshore version on the internet, you're likely to get not much more than a folded page showing how the batteries go in and you turn it on. But you should still learn about using it, and the "Stitch in time" booklet is a good way to do that.

Especially remember this: while you are counting off the seconds it takes for the reading to stabilize, your tester is storing energy in that motor to build up to the tester's 500 or 1000 V output.

That energy is still stored in the motor if you say "ok, I'm done" and unhook the test leads. The motor ... might ... remind you of that later ... if you forget.

Good megohm testers generally have a feature to bleed off the stored charge at the completion of your test, and tell you when it is safe to unhook the leads. But it's up to you to know that feature exists, and know why it's important.