Acclaim that has the engine light on and the voltage gauge has moved a bit

34 is related to the cruise control and 55 is "end of message". There is no code 78.

Now we're making sense. Code 12 just means the ignition switch was turned off. Duh. 17 means the engine was running cold too long. Every Chrysler will have that one in winter because it takes longer than six minutes to reach normal operating temperature. That one won't turn on the Check Engine light so you'll never know it was set. 47 is "system voltage too low". That's why the battery light is on too. The Engine Computer performed a self-test to try to increase the alternator's output voltage and wasn't successful. How do you feel about using an inexpensive digital voltmeter? I can walk you through the steps if necessary. You'll need to measure the battery voltage and the voltages on the two small terminals on the back of the alternator while the engine is running. One of those two will be key in diagnosing the problem which could be a relatively inexpensive repair.

Nope. Disregard code 17. ALL Chryslers will have that one in winter. You MIGHT get valid results with a test light instead of a voltmeter. Does the back of your alternator look similar to the one in this photo? If so, there will be a small black plastic block bolted to it. Wait, I'll post another photo. In the second photo the block has been unbolted but the blue arrow shows what it looks like. The two red arrows show where to measure the voltages. If you use a test light instead, tell me how bright the light is while the engine is running. One terminal should have a bright light. The second one will be either just as bright, out completely, or fairly bright and flickering rapidly.