I am trying to send OBD2 queries to a Chevy Volt while the car is off. I can still get responses when the car is “awake” (for example, if I press the lock or unlock buttons on the key), but after about 30 seconds, it goes back to sleep, and nothing I send will wake it back up.
I can wake up the SWCAN bus by sending almost any frame, which is a start, and when I do that, I see one frame being repeated on CAN0 (ID 0x3ED, 6 bytes, 00 00 00 00 00 FF), which I don’t see when the car wakes up normally.
I have tried sniffing the bus while it is waking up, but I don’t see any special frames being sent, other than the 0x100 frame over SWCAN, which just seems to wake that bus up.
Is there an extra out-of-band signal I need to tap into somehow?