Chasing info code 123 *without* P3000? Or do I need a better scan tool?

I ordered a "Vici" brand VC60B+ from Amazon; it cost me about $43 plus shipping. This same meter is also sold as a Victor, Samyo, Kiamitor, and probably other brands. There are also a few different versions - mine has a rotary range switch, and in addition to the megger functions, also has three "normal" meter ranges - 1000 V DC, 750 V AC, and 2000 ohms. I tested the megger on the bench with some high-value resistors, and compared it with my other meters, and it seemed to be reasonably accurate.

It comes with everything you need, including test leads and AA batteries (which are the cheap "heavy-duty" carbon-zinc type, but seemed to work well enough for me). The test leads are the normal "probe" type that come with regular meters, but they also have some insulated alligator clips that go on the ends - it's probably not a good idea to hold the probes in your hands for the megger tests. The "tail" of the alligator clip is just crimped to make a place for the probe to plug into, so if you plug and unplug the probe a few times, the connection tends to loosen up... using a pair of pliers on the alligator clip to re-crimp it will help.

The high voltage from the meter is current-limited. I discovered that when you are running a megger test, if the meter has not hit the current limit, it will beep intermittently. Once it hits the current limit, it beeps continuously. I think this is designed to tell you that it might not be developing the full rated test voltage. You will probably only run into this if you end up testing the inverter; if your cables and motor windings are in good shape, their resistance to body ground should be high enough that the meter won't go into current limit.

Since you are in Wichita, I guarantee you that somebody at one of the bird works has a megger and knows how to use it. However, they may or may not be able to sneak it out of there at night for ground vehicle repair purposes. But if you do know somebody, asking is free...

Advice: Forget the manual that comes with the meter and go read the book that Chap linked:

Also, go to Youtube and search "VC60B+", and you'll find a few different videos of people using the same meter that I have.

The flowchart in the Black and Teal Book of Truth is quite elaborate, but basically what it boils down to is isolating various parts of the system before megging them. For instance, you disconnect the two high-voltage DC cables at the traction battery, AND at the inverter under the hood, so that both ends of both cables are just hanging in the air. Then, you megger between one cable and body ground, and the other cable and body ground. To check the motor/generators, you disconnect all six motor/generator cables from the inverter, so they are just hanging in the air. Then you megger between one cable end and the transaxle case, and then between the second cable end and the transaxle case, and so on, and finally between the sixth cable end and the transaxle case.

There are some steps in there for megging inside the traction battery, which I didn't do, but you always do it with the thing you're megging disconnected from everything else. Like, if you suspect the service plug and fuse assembly, you disconnect the cables that run to it from the middle two modules, and megger between the cable ends and body ground. There is also a step in there about megging the System Main Relay (the big relay inside the battery - you can hear it click when you turn the ignition key on and off), but again, you disconnect all the high-voltage cables from it, and then megger between the places on the relay where the high-voltage cables connect, and ground.

Important: YOU NEVER HAVE THE IGNITION KEY ON WHEN YOU'RE MEGGING SOMETHING. For the tests inside the HV battery, the manual even specifies that you disconnect the negative cable of the aux (12 V) battery, so nothing inside there can get powered up. The idea is to not accidentally send the 500 volts from the megger into something that only expects 12 volts.

Intermittent problems are "fun", aren't they? Mine has been running with no P3009 for 100+ miles since I put it back together, but then again, it hasn't rained much here. Right now, the best rain chance looks to be this Thursday night, the 20th.

 

Update: I've driven the car about 240 miles since I put it all back together, and P3009 has not returned. A couple of times, I drove it a few hours after it rained, or the day after it rained, and it was OK. Today, it rained this morning, let up in the afternoon, and rained some more in the evening. I started the car in the evening, while it was raining, and no codes - drove it to dinner and back, about 9 miles total, and no codes. So hopefully it is fixed.