Ok, I did the following:

1. I took the sled out of my car.
2. I connected my computer's serial to the sled's serial using a 1on1 cable. I tried to watch the boot-output using hyperterminal. Nothing happened.
3. Same with a crossover cable.
4. In both cases, the player's LED changed from pulsing to flashing.

I used Hijack to force the player in Car/DC mode.