Weird power issue on an aftermarket head unit install

[rslaback]

My son now owns a 2003 Vibe base model that has more red flags than a circus. I've always been the fix it guy around here so I get more projects now.

The stock unit was barely functioning and providing a 500ma parasitic draw so it needed to go. I picked up a fit kit and harness and wired up the adapter to a single DIN unit I had lying around. When I plugged it in I got a faint display from the head unit but not full power. I probed my incoming constant and ignition 12v and those seemed fine as did the ground. I thought maybe there was a short on a speaker backfeeding power but those all checked out ok as well. Here is the weird part: I accidentally found that if the radio is not plugged in when the key is turned but gets plugged in about 15 seconds later then it works fine. Shut the car off and it won't work again when the car is turned on.

This seems odd to me and the only explanation I can think of is that the theftlock system tries to read the VIN off the chip at power on and kills power unless it sees it. If I wait until after the computers full wake then it is fine.

Before I go ahead and just ignore the audio connector wires and run my own 12v source(s) is this a normal phenomenon? Also, it looks like I could steal switched power from the cigarette lighter. Is there a source of constant 12v anywhere close?