Easiest way to confirm P3009 error source

The paragraph below came from; this article I edited it a bit for Gen1 clarity.

The first step is to clear the P3009 trouble code by unhooking the 12V battery for a moment or using a code reader. Now turn the key on/ but NOT start/ready mode, wait 30 seconds and if the code comes back, the leak is in the battery case. If the code does not return, turn key to start to "ready mode" and immediately shift to neutral and stay this mode for 30 seconds. If the code returns, the leak is in the power cables or inverter. If the code did not set, shift to drive and if the code appears now (can take up to a minute or so), the leak is in the transaxle. This is something that can be done in a few minutes without a scan tool or "megger" while never removing any components and not leaving the driver seat.​

Ideally you want 3009 in battery case. That might be fixable without buying anything, just take apart battery and clean bus bars etc. If your bus bars are really "gooey", new ones are available from the dealer for a couple hundred bucks. Inverter is harder to replace, transaxle is the hardest.