I have a Check Engine light on and the radio doesn't work. They may be connected.

First the facts, then the questions:

Monday morning I discovered that I had left the key switch on Accessory and had a dead battery. Tried to jump it-hooked up cables to another car that was idling. The idle slowed a little when I made the final connection. So far OK.

The 240 with the dead battery wouldn't start, but I noticed the alternator was smoking! Removed the cables immediately -- had it towed to a shop. They checked the alt and battery -- everything OK, just needed a battery charge.

Picked it up this morning -- started OK except for the Check Engine light. Checked oil and proceeded to work. No radio. Fuse OK (tried two, both looked OK).

Questions: Can I check the code for the light myself? Could I have blown some kind of fusible link for the radio? In my frustration on Monday morning it's conceivable that I didnt hook up the cables right (I was in one h--- of a hurry). Would the other idling car slowed down if the cables were connected wrong? Help! I know that some of you Volvo wizards have the answers.