drops from 12v on Tx to 0v on Tx. He suggests perhaps the Navman sleeve is keying on this rather than DTR.

Sounds logical.

In other news:

Consistently, leaving the GPS on permanent 12v power for several hours with the empeg unplugged and the car parked outside, then re-inserting the empeg with the no-cold-boot-patch version of GPSapp, results in instantaneous satellite re-acquisition.

The same conditions, when left overnight parked in my garage, results in a full cold boot when I come out the next morning.

Since the garage's metal roof blocks the satellite signals down to unusable levels, I wonder if the unit simply gives up the ghost at some point because of LOS and the software/timing has nothing to do with it. To that end, I have parked the car outdoors tonight to see what it does when I put the player back in tomorrow morning.