1. Have to ask, engine wasn't running when trying to get the codes right? I have 2004, but never had a problem getting codes.

2. I had a similar problem, diagnosis was -> misfires on some plugs, I changed all the plugs and swapped some coils to see if I could find a bad coil. Misfires still occured. I then changed my brand of Gas and I used Techron Fuel Injector cleaner. My misfires went away but I still occassionally have a rough idle.

If a cylinder isn't firing it would be cooler to the touch (don't try this on a really hot engine, maybe use gloves, a thermometer or an Ice cube to find a cold exhaust).