Q: The Malfunction indicator light went on, and won't go off. on 2005 Dodge Grand Caravan

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The Malfunction indicator light went on and I've had it looked at by a mechanic twice. Says he checked on diagnostic machine, and not to worry. When I start it, it runs a little shaky, but then ok when I drive. Should I have it checked out, don't want major engine, transmission, or emission control system damage. The light stays on, it doesn't flash.
(1) Answer
(1) Comments
Well when I turned off and on the ignition 3 times, (what I read I have to do to get the code), it just read "done" which I was confused. I didn't get any P codes like I've been reading from others. The mechanic didn't tell me what codes he saw. I guess I could ask, but did I do it right by turning off and on the ignition 3 times? The odometer read "done". I tried it again and again, but then it didn't give me anything, just the mileage remained. Appreciate your help!

I did the same thing this morning to get the codes, and I got P0302 and then P0304. After reading about it, I guess the last number of the code tells me what cylinder is causing the problem, yes/no?

Thanks for your help!