Re: Cable and software available for MIL codes?
You can get a code reader at most auto parts stores. I bought mine at Advanced Autoparts when the tranny temperature light went on in my Liberty. Think I paid $60; it was on sale for $20 off.
The super cheap ones simply display the code; e.g. "P0279".
A little more money, and they'll give you a brief text description; e.g. "P0279 Torque Converter". Mine does this.
More money than that, they'll give you a explanatory paragraph or sentence or two.
The cheap ones forget the code as soon as you unplug it; they're only powered when plugged in to the car. So you need to remember displayed codes or write them down while it's plugged in. More expensive readers have a battery backup and will remember and let you view the codes after unplugging it and other stuff.
Some will let you see additional info, such as time the error was recorded, temperature of engine at time of error, speed of vehicle, etc. Mine will also do this.
Agreed that they don't always exactly pinpoint the problem. Although it did in my case, I've leant it to my dad and a neighbor and codes were a little vague. But a bit of googling of the codes, along with make/model/year will often get you a lot of valuable info if the code is not an uncommon occurrence for something particular.