From what I gathered, a Warn lockout can happen for a number of reasons completely unrelated to alcohol, if there is an Error light along with it. Blowing too hard, blowing too soft, not blowing steady, not operating the buttons just right. All of these can cause an Error induced lockout.
Even low voltage will, on the LJ-1. No idea if this is the case with other units or not. I don’t know what the voltage range is on the LJ-1, but it shouldn’t be any higher than the low range of a starter. I mean if the battery has enough voltage/amps to crank the car, that should be plently of volts/amps to run the machine. Especially considering nothing else is drawing power at the time of a start up test, except the ECM, clock, radio memory and possibly the interior lights (if at night and you have them on). None of these draw very much power though. The interior lights would draw the most. But I would think, if the machine doesn’t have enough power to run, surely the starter isn’t going to get enough power to crank the car anyway.
They don’t let us know the power requirements of the unit and it is unlawful to test it ourselves. So I have no clue on that one.
I don’t think this is a good idea though, a lockout due to errors that is. It leaves people stranded that are not drinking, just not blowing right or maybe letting off or holding down the button a fraction of a second too long/short, etc. This of course will be something users improve upon with practice, so chances of a lockout because of it are probably very limited after some use. Anyway, it still isn’t a good idea. The machine should only lock a person out, if it detects alcohol. I suppose it has to ‘reboot’ or something after a few errors, not sure though.
As far as DMV, I don’t think a Warn light is any real problem for you, unless it is a Warn light ONLY. As long as the Error is flashing too, it simply means you just didn’t do something exactly right. Don’t sweat it, like I did, it only makes trying to get the thing to work even more difficult, since you may get nervous.
Sad fact, you do something wrong while trying to take the test, you may get a Warn lockout (Warn and Error lights flashing). However, if you get a Warn light, with no Error light (means it detects some alcohol), you can still crank your car and drive off.